### 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)
EDITOR_DEF("interface/inspector/horizontal_vector2_editing", false);
	EDITOR_DEF("interface/inspector/horizontal_vector_types_editing", true);
	EDITOR_DEF("interface/inspector/open_resources_in_current_inspector", true);
	PackedStringArray open_in_new_inspector_defaults;
	
	open_in_new_inspector_defaults.push_back("Script");
	
	open_in_new_inspector_defaults.push_back("MeshLibrary");
	EDITOR_DEF("interface/inspector/resources_to_open_in_new_inspector", open_in_new_inspector_defaults);
	EDITOR_DEF("interface/inspector/default_color_picker_mode", 0);
	EditorSettings::get_singleton()->add_property_hint(PropertyInfo(Variant::INT, "interface/inspector/default_color_picker_mode", PROPERTY_HINT_ENUM, "RGB,HSV,RAW,OKHSL", PROPERTY_USAGE_DEFAULT));
	EDITOR_DEF("interface/inspector/default_color_picker_shape", (int32_t)ColorPicker::SHAPE_OKHSL_CIRCLE);
	EditorSettings::get_singleton()->add_property_hint(PropertyInfo(Variant::INT, "interface/inspector/default_color_picker_shape", PROPERTY_HINT_ENUM, "HSV Rectangle,HSV Rectangle Wheel,VHS Circle,OKHSL Circle", PROPERTY_USAGE_DEFAULT));
	ED_SHORTCUT("canvas_item_editor/pan_view", TTR("Pan View"), Key::SPACE);
	const Vector<String> textfile_ext = ((String)(EDITOR_GET("docks/filesystem/textfile_extensions"))).split(",", false);
	for (const String &E : textfile_ext) {
		textfile_extensions.insert(E);
	}
	resource_preview = memnew(EditorResourcePreview);
	add_child(resource_preview);
	progress_dialog = memnew(ProgressDialog);
	progress_dialog->set_unparent_when_invisible(true);
	gui_base = memnew(Panel);
	add_child(gui_base);
	
	gui_base->set_anchors_and_offsets_preset(Control::PRESET_FULL_RECT);
	gui_base->set_anchor(SIDE_RIGHT, Control::ANCHOR_END);
	gui_base->set_anchor(SIDE_BOTTOM, Control::ANCHOR_END);
	gui_base->set_end(Point2(0, 0));
	main_vbox = memnew(VBoxContainer);