KCL: Use named fields for KclError (#7321)

We've changed the unnamed field of `KclError` variants to a named called `details`.

To clarify: previously KCL errors looked like this:

```rust
pub enum KclError {
    Lexical(KclErrorDetails),
    Syntax(KclErrorDetails),
```

Now they look like this:

```rust
pub enum KclError {
    Lexical { details: KclErrorDetails },
    Syntax { details: KclErrorDetails },
}
```

This lets us more easily add fields to the errors. For example, in the UndefinedValue case, adding a field for what the undefined name was. This PR refactors the code to make my PR in https://github.com/KittyCAD/modeling-app/pull/7309 much easier.

Pure refactor, should not change any behaviour.

rust/kcl-lib/src/std/clone.rs

@@ -84,7 +84,7 @@ async fn inner_clone(
     fix_tags_and_references(&mut new_geometry, old_id, exec_state, &args)
         .await
         .map_err(|e| {
-            KclError::Internal(KclErrorDetails::new(
+            KclError::new_internal(KclErrorDetails::new(
                 format!("failed to fix tags and references: {:?}", e),
                 vec![args.source_range],
             ))