### 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)
initialize_modules(MODULE_INITIALIZATION_LEVEL_EDITOR);
	GDExtensionManager::get_singleton()->initialize_extensions(GDExtension::INITIALIZATION_LEVEL_EDITOR);
	ClassDB::set_current_api(ClassDB::API_CORE);
#endif
	MAIN_PRINT("Main: Load Modules");
	register_platform_apis();
	GLOBAL_DEF_BASIC(PropertyInfo(Variant::STRING, "display/mouse_cursor/custom_image", PROPERTY_HINT_FILE, "*.png,*.webp"), String());
	GLOBAL_DEF_BASIC("display/mouse_cursor/custom_image_hotspot", Vector2());
	GLOBAL_DEF_BASIC("display/mouse_cursor/tooltip_position_offset", Point2(10, 10));
	if (String(GLOBAL_GET("display/mouse_cursor/custom_image")) != String()) {
		Ref<Texture2D> cursor = ResourceLoader::load(
				GLOBAL_GET("display/mouse_cursor/custom_image"));
		if (cursor.is_valid()) {
			Vector2 hotspot = GLOBAL_GET("display/mouse_cursor/custom_image_hotspot");
			Input::get_singleton()->set_custom_mouse_cursor(cursor, Input::CURSOR_ARROW, hotspot);
		}
	}
	camera_server = CameraServer::create();
	MAIN_PRINT("Main: Load Physics");
	initialize_physics();
	initialize_navigation_server();
	register_server_singletons();
	/
	ScriptServer::init_languages();
	theme_db->initialize_theme();
	audio_server->load_default_bus_layout();
#if defined(MODULE_MONO_ENABLED) && defined(TOOLS_ENABLED)
	/
	/
	/