Reuse Closure type in Value::Closure (#10894)

# Description
Reuses the existing `Closure` type in `Value::Closure`. This will help
with the span refactoring for `Value`. Additionally, this allows us to
more easily box or unbox the `Closure` case should we chose to do so in
the future.

# User-Facing Changes
Breaking API change for `nu_protocol`.

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

@@ -142,7 +142,7 @@ fn local_into_string(value: Value, separator: &str, config: &Config) -> String {
             Err(error) => format!("{error:?}"),
         },
         Value::Block { val, .. } => format!("<Block {val}>"),
-        Value::Closure { val, .. } => format!("<Closure {val}>"),
+        Value::Closure { val, .. } => format!("<Closure {}>", val.block_id),
         Value::Nothing { .. } => String::new(),
         Value::Error { error, .. } => format!("{error:?}"),
         Value::Binary { val, .. } => format!("{val:?}"),