Rename Value::CustomValue to Value::Custom (#12309)

# Description
The second `Value` is redundant and will consume five extra bytes on
each transmission of a custom value to/from a plugin.

# User-Facing Changes
This is a breaking change to the plugin protocol.

The [example in the protocol
reference](https://www.nushell.sh/contributor-book/plugin_protocol_reference.html#value)
becomes

```json
{
  "Custom": {
    "val": {
      "type": "PluginCustomValue",
      "name": "database",
      "data": [36, 190, 127, 40, 12, 3, 46, 83],
      "notify_on_drop": true
    },
    "span": {
      "start": 320,
      "end": 340
    }
  }
}
```

instead of 

```json
{
  "CustomValue": {
    ...
  }
}
```


# After Submitting
Update plugin protocol reference

crates/nu-cmd-dataframe/src/dataframe/eager/query_df.rs

@@ -87,7 +87,7 @@ fn command(
     let lazy = NuLazyFrame::new(false, df_sql);
 
     let eager = lazy.collect(call.head)?;
-    let value = Value::custom_value(Box::new(eager), call.head);
+    let value = Value::custom(Box::new(eager), call.head);
 
     Ok(PipelineData::Value(value, None))
 }

crates/nu-cmd-dataframe/src/dataframe/lazy/collect.rs

@@ -55,7 +55,7 @@ impl Command for LazyCollect {
     ) -> Result<PipelineData, ShellError> {
         let lazy = NuLazyFrame::try_from_pipeline(input, call.head)?;
         let eager = lazy.collect(call.head)?;
-        let value = Value::custom_value(Box::new(eager), call.head);
+        let value = Value::custom(Box::new(eager), call.head);
 
         Ok(PipelineData::Value(value, None))
     }

crates/nu-cmd-dataframe/src/dataframe/lazy/to_lazy.rs

@@ -47,7 +47,7 @@ impl Command for ToLazyFrame {
 
         let df = NuDataFrame::try_from_iter(input.into_iter(), maybe_schema)?;
         let lazy = NuLazyFrame::from_dataframe(df);
-        let value = Value::custom_value(Box::new(lazy), call.head);
+        let value = Value::custom(Box::new(lazy), call.head);
 
         Ok(PipelineData::Value(value, None))
     }

crates/nu-cmd-dataframe/src/dataframe/values/nu_dataframe/custom_value.rs

@@ -17,7 +17,7 @@ impl CustomValue for NuDataFrame {
             from_lazy: false,
         };
 
-        Value::custom_value(Box::new(cloned), span)
+        Value::custom(Box::new(cloned), span)
     }
 
     fn type_name(&self) -> String {
@@ -55,7 +55,7 @@ impl CustomValue for NuDataFrame {
 
     fn partial_cmp(&self, other: &Value) -> Option<std::cmp::Ordering> {
         match other {
-            Value::CustomValue { val, .. } => val
+            Value::Custom { val, .. } => val
                 .as_any()
                 .downcast_ref::<Self>()
                 .and_then(|other| self.is_equal(other)),

crates/nu-cmd-dataframe/src/dataframe/values/nu_dataframe/mod.rs

@@ -116,15 +116,15 @@ impl NuDataFrame {
     }
 
     pub fn dataframe_into_value(dataframe: DataFrame, span: Span) -> Value {
-        Value::custom_value(Box::new(Self::new(false, dataframe)), span)
+        Value::custom(Box::new(Self::new(false, dataframe)), span)
     }
 
     pub fn into_value(self, span: Span) -> Value {
         if self.from_lazy {
             let lazy = NuLazyFrame::from_dataframe(self);
-            Value::custom_value(Box::new(lazy), span)
+            Value::custom(Box::new(lazy), span)
         } else {
-            Value::custom_value(Box::new(self), span)
+            Value::custom(Box::new(self), span)
         }
     }
 
@@ -152,7 +152,7 @@ impl NuDataFrame {
 
         for value in iter {
             match value {
-                Value::CustomValue { .. } => return Self::try_from_value(value),
+                Value::Custom { .. } => return Self::try_from_value(value),
                 Value::List { vals, .. } => {
                     let record = vals
                         .into_iter()
@@ -256,7 +256,7 @@ impl NuDataFrame {
     pub fn get_df(value: Value) -> Result<Self, ShellError> {
         let span = value.span();
         match value {
-            Value::CustomValue { val, .. } => match val.as_any().downcast_ref::<Self>() {
+            Value::Custom { val, .. } => match val.as_any().downcast_ref::<Self>() {
                 Some(df) => Ok(NuDataFrame {
                     df: df.df.clone(),
                     from_lazy: false,
@@ -283,7 +283,7 @@ impl NuDataFrame {
     }
 
     pub fn can_downcast(value: &Value) -> bool {
-        if let Value::CustomValue { val, .. } = value {
+        if let Value::Custom { val, .. } = value {
             val.as_any().downcast_ref::<Self>().is_some()
         } else {
             false

crates/nu-cmd-dataframe/src/dataframe/values/nu_dataframe/operations.rs

@@ -20,7 +20,7 @@ impl NuDataFrame {
     ) -> Result<Value, ShellError> {
         let rhs_span = right.span();
         match right {
-            Value::CustomValue { val: rhs, .. } => {
+            Value::Custom { val: rhs, .. } => {
                 let rhs = rhs.as_any().downcast_ref::<NuDataFrame>().ok_or_else(|| {
                     ShellError::DowncastNotPossible {
                         msg: "Unable to create dataframe".to_string(),

crates/nu-cmd-dataframe/src/dataframe/values/nu_expression/custom_value.rs

@@ -19,7 +19,7 @@ impl CustomValue for NuExpression {
     fn clone_value(&self, span: nu_protocol::Span) -> Value {
         let cloned = NuExpression(self.0.clone());
 
-        Value::custom_value(Box::new(cloned), span)
+        Value::custom(Box::new(cloned), span)
     }
 
     fn type_name(&self) -> String {
@@ -54,7 +54,7 @@ fn compute_with_value(
 ) -> Result<Value, ShellError> {
     let rhs_span = right.span();
     match right {
-        Value::CustomValue { val: rhs, .. } => {
+        Value::Custom { val: rhs, .. } => {
             let rhs = rhs.as_any().downcast_ref::<NuExpression>().ok_or_else(|| {
                 ShellError::DowncastNotPossible {
                     msg: "Unable to create expression".into(),

crates/nu-cmd-dataframe/src/dataframe/values/nu_expression/mod.rs

@@ -55,13 +55,13 @@ impl From<Expr> for NuExpression {
 
 impl NuExpression {
     pub fn into_value(self, span: Span) -> Value {
-        Value::custom_value(Box::new(self), span)
+        Value::custom(Box::new(self), span)
     }
 
     pub fn try_from_value(value: Value) -> Result<Self, ShellError> {
         let span = value.span();
         match value {
-            Value::CustomValue { val, .. } => match val.as_any().downcast_ref::<Self>() {
+            Value::Custom { val, .. } => match val.as_any().downcast_ref::<Self>() {
                 Some(expr) => Ok(NuExpression(expr.0.clone())),
                 None => Err(ShellError::CantConvert {
                     to_type: "lazy expression".into(),
@@ -90,7 +90,7 @@ impl NuExpression {
 
     pub fn can_downcast(value: &Value) -> bool {
         match value {
-            Value::CustomValue { val, .. } => val.as_any().downcast_ref::<Self>().is_some(),
+            Value::Custom { val, .. } => val.as_any().downcast_ref::<Self>().is_some(),
             Value::List { vals, .. } => vals.iter().all(Self::can_downcast),
             Value::String { .. } | Value::Int { .. } | Value::Bool { .. } | Value::Float { .. } => {
                 true
@@ -144,7 +144,7 @@ impl ExtractedExpr {
     fn extract_exprs(value: Value) -> Result<ExtractedExpr, ShellError> {
         match value {
             Value::String { val, .. } => Ok(ExtractedExpr::Single(col(val.as_str()))),
-            Value::CustomValue { .. } => NuExpression::try_from_value(value)
+            Value::Custom { .. } => NuExpression::try_from_value(value)
                 .map(NuExpression::into_polars)
                 .map(ExtractedExpr::Single),
             Value::List { vals, .. } => vals

crates/nu-cmd-dataframe/src/dataframe/values/nu_lazyframe/custom_value.rs

@@ -18,7 +18,7 @@ impl CustomValue for NuLazyFrame {
             schema: self.schema.clone(),
         };
 
-        Value::custom_value(Box::new(cloned), span)
+        Value::custom(Box::new(cloned), span)
     }
 
     fn type_name(&self) -> String {

crates/nu-cmd-dataframe/src/dataframe/values/nu_lazyframe/mod.rs

@@ -90,9 +90,9 @@ impl NuLazyFrame {
     pub fn into_value(self, span: Span) -> Result<Value, ShellError> {
         if self.from_eager {
             let df = self.collect(span)?;
-            Ok(Value::custom_value(Box::new(df), span))
+            Ok(Value::custom(Box::new(df), span))
         } else {
-            Ok(Value::custom_value(Box::new(self), span))
+            Ok(Value::custom(Box::new(self), span))
         }
     }
 
@@ -141,7 +141,7 @@ impl NuLazyFrame {
     pub fn get_lazy_df(value: Value) -> Result<Self, ShellError> {
         let span = value.span();
         match value {
-            Value::CustomValue { val, .. } => match val.as_any().downcast_ref::<Self>() {
+            Value::Custom { val, .. } => match val.as_any().downcast_ref::<Self>() {
                 Some(expr) => Ok(Self {
                     lazy: expr.lazy.clone(),
                     from_eager: false,
@@ -164,7 +164,7 @@ impl NuLazyFrame {
     }
 
     pub fn can_downcast(value: &Value) -> bool {
-        if let Value::CustomValue { val, .. } = value {
+        if let Value::Custom { val, .. } = value {
             val.as_any().downcast_ref::<Self>().is_some()
         } else {
             false

crates/nu-cmd-dataframe/src/dataframe/values/nu_lazygroupby/custom_value.rs

@@ -18,7 +18,7 @@ impl CustomValue for NuLazyGroupBy {
             from_eager: self.from_eager,
         };
 
-        Value::custom_value(Box::new(cloned), span)
+        Value::custom(Box::new(cloned), span)
     }
 
     fn type_name(&self) -> String {

crates/nu-cmd-dataframe/src/dataframe/values/nu_lazygroupby/mod.rs

@@ -74,7 +74,7 @@ impl From<LazyGroupBy> for NuLazyGroupBy {
 
 impl NuLazyGroupBy {
     pub fn into_value(self, span: Span) -> Value {
-        Value::custom_value(Box::new(self), span)
+        Value::custom(Box::new(self), span)
     }
 
     pub fn into_polars(self) -> LazyGroupBy {
@@ -84,7 +84,7 @@ impl NuLazyGroupBy {
     pub fn try_from_value(value: Value) -> Result<Self, ShellError> {
         let span = value.span();
         match value {
-            Value::CustomValue { val, .. } => match val.as_any().downcast_ref::<NuLazyGroupBy>() {
+            Value::Custom { val, .. } => match val.as_any().downcast_ref::<NuLazyGroupBy>() {
                 Some(group) => Ok(Self {
                     group_by: group.group_by.clone(),
                     schema: group.schema.clone(),

crates/nu-cmd-dataframe/src/dataframe/values/nu_when/custom_value.rs

@@ -14,7 +14,7 @@ impl CustomValue for NuWhen {
     fn clone_value(&self, span: nu_protocol::Span) -> Value {
         let cloned = self.clone();
 
-        Value::custom_value(Box::new(cloned), span)
+        Value::custom(Box::new(cloned), span)
     }
 
     fn type_name(&self) -> String {

crates/nu-cmd-dataframe/src/dataframe/values/nu_when/mod.rs

@@ -51,13 +51,13 @@ impl From<ChainedThen> for NuWhen {
 
 impl NuWhen {
     pub fn into_value(self, span: Span) -> Value {
-        Value::custom_value(Box::new(self), span)
+        Value::custom(Box::new(self), span)
     }
 
     pub fn try_from_value(value: Value) -> Result<Self, ShellError> {
         let span = value.span();
         match value {
-            Value::CustomValue { val, .. } => match val.as_any().downcast_ref::<Self>() {
+            Value::Custom { val, .. } => match val.as_any().downcast_ref::<Self>() {
                 Some(expr) => Ok(expr.clone()),
                 None => Err(ShellError::CantConvert {
                     to_type: "when expression".into(),