### 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)
}
	help_menu->set_item_icon(help_menu->get_item_index(HELP_SEARCH), theme->get_icon(SNAME("HelpSearch"), EditorStringName(EditorIcons)));
	help_menu->set_item_icon(help_menu->get_item_index(HELP_DOCS), theme->get_icon(SNAME("ExternalLink"), EditorStringName(EditorIcons)));
	help_menu->set_item_icon(help_menu->get_item_index(HELP_QA), theme->get_icon(SNAME("ExternalLink"), EditorStringName(EditorIcons)));
	help_menu->set_item_icon(help_menu->get_item_index(HELP_REPORT_A_BUG), theme->get_icon(SNAME("ExternalLink"), EditorStringName(EditorIcons)));
	help_menu->set_item_icon(help_menu->get_item_index(HELP_COPY_SYSTEM_INFO), theme->get_icon(SNAME("ActionCopy"), EditorStringName(EditorIcons)));
	help_menu->set_item_icon(help_menu->get_item_index(HELP_SUGGEST_A_FEATURE), theme->get_icon(SNAME("ExternalLink"), EditorStringName(EditorIcons)));
	help_menu->set_item_icon(help_menu->get_item_index(HELP_SEND_DOCS_FEEDBACK), theme->get_icon(SNAME("ExternalLink"), EditorStringName(EditorIcons)));
	help_menu->set_item_icon(help_menu->get_item_index(HELP_COMMUNITY), theme->get_icon(SNAME("ExternalLink"), EditorStringName(EditorIcons)));
	help_menu->set_item_icon(help_menu->get_item_index(HELP_ABOUT), theme->get_icon(SNAME("Godot"), EditorStringName(EditorIcons)));
	help_menu->set_item_icon(help_menu->get_item_index(HELP_SUPPORT_GODOT_DEVELOPMENT), theme->get_icon(SNAME("Heart"), EditorStringName(EditorIcons)));
	for (int i = 0; i < main_editor_buttons.size(); i++) {
		main_editor_buttons.write[i]->add_theme_font_override("font", theme->get_font(SNAME("main_button_font"), EditorStringName(EditorFonts)));
		main_editor_buttons.write[i]->add_theme_font_size_override("font_size", theme->get_font_size(SNAME("main_button_font_size"), EditorStringName(EditorFonts)));
	}
	if (EditorDebuggerNode::get_singleton()->is_visible()) {
		bottom_panel->add_theme_style_override("panel", theme->get_stylebox(SNAME("BottomPanelDebuggerOverride"), EditorStringName(EditorStyles)));
	}
	for (int i = 0; i < main_editor_buttons.size(); i++) {
		Button *tb = main_editor_buttons[i];
		EditorPlugin *p_editor = editor_table[i];
		Ref<Texture2D> icon = p_editor->get_icon();
		if (icon.is_valid()) {
			tb->set_icon(icon);
		} else if (theme->has_icon(p_editor->get_name(), EditorStringName(EditorIcons))) {
			tb->set_icon(theme->get_icon(p_editor->get_name(), EditorStringName(EditorIcons)));
		}
	}
}
void EditorNode::update_preview_themes(int p_mode) {