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-command/src/conversions/into/string.rs

@@ -226,7 +226,7 @@ fn action(input: &Value, args: &Arguments, span: Span) -> Value {
             },
             span,
         ),
-        Value::CustomValue { val, .. } => {
+        Value::Custom { val, .. } => {
             // Only custom values that have a base value that can be converted to string are
             // accepted.
             val.to_base_value(input.span())

crates/nu-command/src/database/values/sqlite.rs

@@ -69,7 +69,7 @@ impl SQLiteDatabase {
     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(db) => Ok(Self {
                     path: db.path.clone(),
                     ctrlc: db.ctrlc.clone(),
@@ -97,7 +97,7 @@ impl SQLiteDatabase {
 
     pub fn into_value(self, span: Span) -> Value {
         let db = Box::new(self);
-        Value::custom_value(db, span)
+        Value::custom(db, span)
     }
 
     pub fn query(
@@ -357,7 +357,7 @@ impl CustomValue for SQLiteDatabase {
             ctrlc: self.ctrlc.clone(),
         };
 
-        Value::custom_value(Box::new(cloned), span)
+        Value::custom(Box::new(cloned), span)
     }
 
     fn type_name(&self) -> String {

crates/nu-command/src/debug/explain.rs

@@ -293,7 +293,7 @@ pub fn debug_string_without_formatting(value: &Value) -> String {
         Value::CellPath { val, .. } => val.to_string(),
         // If we fail to collapse the custom value, just print <{type_name}> - failure is not
         // that critical here
-        Value::CustomValue { val, .. } => val
+        Value::Custom { val, .. } => val
             .to_base_value(value.span())
             .map(|val| debug_string_without_formatting(&val))
             .unwrap_or_else(|_| format!("<{}>", val.type_name())),

crates/nu-command/src/filters/columns.rs

@@ -94,7 +94,7 @@ fn getcol(
                         .into_pipeline_data(ctrlc)
                         .set_metadata(metadata))
                 }
-                Value::CustomValue { val, .. } => {
+                Value::Custom { val, .. } => {
                     // TODO: should we get CustomValue to expose columns in a more efficient way?
                     // Would be nice to be able to get columns without generating the whole value
                     let input_as_base_value = val.to_base_value(span)?;

crates/nu-command/src/filters/find.rs

@@ -531,7 +531,7 @@ fn value_should_be_printed(
         | Value::Glob { .. }
         | Value::List { .. }
         | Value::CellPath { .. }
-        | Value::CustomValue { .. } => term_contains_value(term, &lower_value, span),
+        | Value::Custom { .. } => term_contains_value(term, &lower_value, span),
         Value::Record { val, .. } => {
             record_matches_term(val, columns_to_search, filter_config, term, span)
         }

crates/nu-command/src/filters/values.rs

@@ -147,7 +147,7 @@ fn values(
                         .into_pipeline_data_with_metadata(metadata, ctrlc)),
                     Err(err) => Err(err),
                 },
-                Value::CustomValue { val, .. } => {
+                Value::Custom { val, .. } => {
                     let input_as_base_value = val.to_base_value(span)?;
                     match get_values(&[input_as_base_value], head, span) {
                         Ok(cols) => Ok(cols

crates/nu-command/src/formats/to/delimited.rs

@@ -115,7 +115,7 @@ fn to_string_tagged_value(
         | Value::Int { .. }
         | Value::Duration { .. }
         | Value::Binary { .. }
-        | Value::CustomValue { .. }
+        | Value::Custom { .. }
         | Value::Filesize { .. }
         | Value::CellPath { .. }
         | Value::Float { .. } => Ok(v.clone().to_abbreviated_string(config)),

crates/nu-command/src/formats/to/json.rs

@@ -139,7 +139,7 @@ pub fn value_to_json_value(v: &Value) -> Result<nu_json::Value, ShellError> {
             let collected = val.collect()?;
             value_to_json_value(&collected)?
         }
-        Value::CustomValue { val, .. } => {
+        Value::Custom { val, .. } => {
             let collected = val.to_base_value(span)?;
             value_to_json_value(&collected)?
         }

crates/nu-command/src/formats/to/nuon.rs

@@ -158,7 +158,7 @@ pub fn value_to_string(
             msg_span: span,
             input_span: v.span(),
         }),
-        Value::CustomValue { .. } => Err(ShellError::UnsupportedInput {
+        Value::Custom { .. } => Err(ShellError::UnsupportedInput {
             msg: "custom values are currently not nuon-compatible".to_string(),
             input: "value originates from here".into(),
             msg_span: span,

crates/nu-command/src/formats/to/text.rs

@@ -147,7 +147,7 @@ fn local_into_string(value: Value, separator: &str, config: &Config) -> String {
         Value::CellPath { val, .. } => val.to_string(),
         // If we fail to collapse the custom value, just print <{type_name}> - failure is not
         // that critical here
-        Value::CustomValue { val, .. } => val
+        Value::Custom { val, .. } => val
             .to_base_value(span)
             .map(|val| local_into_string(val, separator, config))
             .unwrap_or_else(|_| format!("<{}>", val.type_name())),

crates/nu-command/src/formats/to/toml.rs

@@ -93,7 +93,7 @@ fn helper(engine_state: &EngineState, v: &Value) -> Result<toml::Value, ShellErr
                 })
                 .collect::<Result<Vec<toml::Value>, ShellError>>()?,
         ),
-        Value::CustomValue { .. } => toml::Value::String("<Custom Value>".to_string()),
+        Value::Custom { .. } => toml::Value::String("<Custom Value>".to_string()),
     })
 }
 

crates/nu-command/src/formats/to/yaml.rs

@@ -95,7 +95,7 @@ pub fn value_to_yaml_value(v: &Value) -> Result<serde_yaml::Value, ShellError> {
                 })
                 .collect::<Result<Vec<serde_yaml::Value>, ShellError>>()?,
         ),
-        Value::CustomValue { .. } => serde_yaml::Value::Null,
+        Value::Custom { .. } => serde_yaml::Value::Null,
     })
 }
 

crates/nu-command/src/sort_utils.rs

@@ -30,7 +30,7 @@ pub fn sort_value(
 
             Ok(Value::list(vals, span))
         }
-        Value::CustomValue { val, .. } => {
+        Value::Custom { val, .. } => {
             let base_val = val.to_base_value(span)?;
             sort_value(&base_val, sort_columns, ascending, insensitive, natural)
         }

crates/nu-command/src/stor/create.rs

@@ -58,7 +58,7 @@ impl Command for StorCreate {
 
         process(table_name, span, &db, columns)?;
         // dbg!(db.clone());
-        Ok(Value::custom_value(db, span).into_pipeline_data())
+        Ok(Value::custom(db, span).into_pipeline_data())
     }
 }
 

crates/nu-command/src/stor/delete.rs

@@ -117,7 +117,7 @@ impl Command for StorDelete {
             }
         }
         // dbg!(db.clone());
-        Ok(Value::custom_value(db, span).into_pipeline_data())
+        Ok(Value::custom(db, span).into_pipeline_data())
     }
 }
 

crates/nu-command/src/stor/export.rs

@@ -73,7 +73,7 @@ impl Command for StorExport {
                 })?;
         }
         // dbg!(db.clone());
-        Ok(Value::custom_value(db, span).into_pipeline_data())
+        Ok(Value::custom(db, span).into_pipeline_data())
     }
 }
 

crates/nu-command/src/stor/import.rs

@@ -71,7 +71,7 @@ impl Command for StorImport {
                 })?;
         }
         // dbg!(db.clone());
-        Ok(Value::custom_value(db, span).into_pipeline_data())
+        Ok(Value::custom(db, span).into_pipeline_data())
     }
 }
 

crates/nu-command/src/stor/insert.rs

@@ -131,7 +131,7 @@ impl Command for StorInsert {
             };
         }
         // dbg!(db.clone());
-        Ok(Value::custom_value(db, span).into_pipeline_data())
+        Ok(Value::custom(db, span).into_pipeline_data())
     }
 }
 

crates/nu-command/src/stor/reset.rs

@@ -55,7 +55,7 @@ impl Command for StorReset {
                 })?;
         }
         // dbg!(db.clone());
-        Ok(Value::custom_value(db, span).into_pipeline_data())
+        Ok(Value::custom(db, span).into_pipeline_data())
     }
 }
 

crates/nu-command/src/stor/update.rs

@@ -143,7 +143,7 @@ impl Command for StorUpdate {
             };
         }
         // dbg!(db.clone());
-        Ok(Value::custom_value(db, span).into_pipeline_data())
+        Ok(Value::custom(db, span).into_pipeline_data())
     }
 }
 

crates/nu-command/src/viewers/table.rs

@@ -403,7 +403,7 @@ fn handle_table_command(
             // instead of stdout.
             Err(*error)
         }
-        PipelineData::Value(Value::CustomValue { val, .. }, ..) => {
+        PipelineData::Value(Value::Custom { val, .. }, ..) => {
             let base_pipeline = val.to_base_value(span)?.into_pipeline_data();
             Table.run(input.engine_state, input.stack, input.call, base_pipeline)
         }