### 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)
return ext_icon;
	}
	
	
	const EditorData::CustomType *ctype = ed.get_custom_type_by_name(p_class);
	if (ctype && ctype->icon.is_valid()) {
		return ctype->icon;
	}
	
	
	if (theme.is_valid()) {
		if (theme->has_icon(p_class, EditorStringName(EditorIcons))) {
			return theme->get_icon(p_class, EditorStringName(EditorIcons));
		}
		if (!p_fallback.is_empty() && theme->has_icon(p_fallback, EditorStringName(EditorIcons))) {
			return theme->get_icon(p_fallback, EditorStringName(EditorIcons));
		}
		
		if (ClassDB::class_exists(p_class)) {
			bool instantiable = !ClassDB::is_virtual(p_class) && ClassDB::can_instantiate(p_class);
			if (ClassDB::is_parent_class(p_class, SNAME("Node"))) {
				return theme->get_icon(instantiable ? "Node" : "NodeDisabled", EditorStringName(EditorIcons));
			} else {
				return theme->get_icon(instantiable ? "Object" : "ObjectDisabled", EditorStringName(EditorIcons));
			}
		}
	}
	return nullptr;
}
Ref<Texture2D> EditorNode::get_object_icon(const Object *p_object, const String &p_fallback) {