### Godot version

4.1.3

### System information

Linux

### Issue description

I'm trying to make an editor plugin on Rust:

```rust
#[derive(GodotClass)]
#[class(tool, editor_plugin, init, base=EditorPlugin)]
pub struct MyEditorPluginBase {}
```

But due to some limitations, I still have to use GDScript for some specific things.

So I tried to make a subclass of this Rust class:

```gdscript
@tool
class_name MyEditorPlugin
extends MyEditorPluginBase
```

This would work if `MyEditorPluginBase` was a GDScript class, but since it's a GDExtension class in my case, it doesn't work:

> Unable to load addon script from path: 'res://addons/my_addon/my_editor_plugin.gd' Base type is not EditorPlugin.

But it obviously **IS** EditorPlugin!

![godot-editorplugin-docs](https://github.com/godotengine/godot/assets/3236464/4665deeb-30f0-45cd-bfff-56101b9d4875)

![godot-editorplugin](https://github.com/godotengine/godot/assets/3236464/b1b6ecb4-de22-4abd-91a3-e180691f67ee)

If I understand correctly, this behavior is caused by this function, which checks some mysterious "instance base type" instead of real inheritance:

https://github.com/godotengine/godot/blob/fa4a65387ea41506ecc519fc61a06da110dce51c/editor/editor_node.cpp#L3456-L3458

https://github.com/godotengine/godot/blob/fa4a65387ea41506ecc519fc61a06da110dce51c/modules/gdscript/gdscript.cpp#L260-L263

Since the [documentation](https://docs.godotengine.org/en/stable/tutorials/plugins/editor/making_plugins.html#the-script-file) doesn't say that the script must be a **direct** subclass of EditorPlugin (and an indirect subclass works fine in GDScript), I interpret this behavior as a Godot bug.

### Steps to reproduce

See above

### Minimal reproduction project

[gdext_editor_plugin_test.zip](https://github.com/godotengine/godot/files/13451014/gdext_editor_plugin_test.zip)
for (int i = 0; i < p_node->get_child_count(); i++) {
		AnimationMixer *mixer = Object::cast_to<AnimationMixer>(p_node->get_child(i));
		if (mixer && mixer->is_reset_on_save_enabled() && mixer->can_apply_reset()) {
			Ref<AnimatedValuesBackup> backup = mixer->apply_reset();
			if (backup.is_valid()) {
				Pair<AnimationMixer *, Ref<AnimatedValuesBackup>> pair;
				pair.first = mixer;
				pair.second = backup;
				r_anim_backups->push_back(pair);
			}
		}
		_reset_animation_mixers(p_node->get_child(i), r_anim_backups);
	}
}
void EditorNode::_save_scene(String p_file, int idx) {
	if (!saving_scene.is_empty() && saving_scene == p_file) {
		return;
	}
	Node *scene = editor_data.get_edited_scene_root(idx);
	if (!scene) {
		show_accept(TTR("This operation can't be done without a tree root."), TTR("OK"));
		return;
	}
	if (!scene->get_scene_file_path().is_empty() && _validate_scene_recursive(scene->get_scene_file_path(), scene)) {
		show_accept(TTR("This scene can't be saved because there is a cyclic instance inclusion.\nPlease resolve it and then attempt to save again."), TTR("OK"));
		return;
	}
	scene->propagate_notification(NOTIFICATION_EDITOR_PRE_SAVE);
	editor_data.apply_changes_in_editors();
	List<Pair<AnimationMixer *, Ref<AnimatedValuesBackup>>> anim_backups;