Add Filesize type (#14369)

# Description
Adds a new `Filesize` type so that `FromValue` can be used to convert a
`Value::Filesize` to a `Filesize`. Currently, to extract a filesize from
a `Value` using `FromValue`, you have to extract an `i64` which coerces
`Value::Int`, `Value::Duration`, and `Value::Filesize` to an `i64`.

Having a separate type also allows us to enforce checked math to catch
overflows. Similarly, it allows us to specify other trait
implementations like `Display` in a common place.

# User-Facing Changes
Multiplication with filesizes now error on overflow. Should not be a
breaking change for plugins (i.e., serialization) since `Filesize` is
marked with `serde(transparent)`.

# Tests + Formatting
Updated some tests.

crates/nu-command/src/math/avg.rs

@@ -90,7 +90,7 @@ pub fn average(values: &[Value], span: Span, head: Span) -> Result<Value, ShellE
     let total = &sum(Value::int(0, head), values.to_vec(), span, head)?;
     let span = total.span();
     match total {
-        Value::Filesize { val, .. } => Ok(Value::filesize(val / values.len() as i64, span)),
+        Value::Filesize { val, .. } => Ok(Value::filesize(val.get() / values.len() as i64, span)),
         Value::Duration { val, .. } => Ok(Value::duration(val / values.len() as i64, span)),
         _ => total.div(head, &Value::int(values.len() as i64, head), head),
     }

crates/nu-command/src/math/mode.rs

@@ -142,9 +142,10 @@ pub fn mode(values: &[Value], _span: Span, head: Span) -> Result<Value, ShellErr
             Value::Float { val, .. } => {
                 Ok(HashableType::new(val.to_ne_bytes(), NumberTypes::Float))
             }
-            Value::Filesize { val, .. } => {
-                Ok(HashableType::new(val.to_ne_bytes(), NumberTypes::Filesize))
-            }
+            Value::Filesize { val, .. } => Ok(HashableType::new(
+                val.get().to_ne_bytes(),
+                NumberTypes::Filesize,
+            )),
             Value::Error { error, .. } => Err(*error.clone()),
             other => Err(ShellError::UnsupportedInput {
                 msg: "Unable to give a result with this input".to_string(),