### 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)
Vector<Node *> nodes = _find_all_node_for_script(base, base, script);
	HashSet<StringName> methods_found;
	for (int i = 0; i < nodes.size(); i++) {
		List<Connection> signal_connections;
		nodes[i]->get_signals_connected_to_this(&signal_connections);
		for (const Connection &connection : signal_connections) {
			if (!(connection.flags & CONNECT_PERSIST)) {
				continue;
			}
			
			Node *source = Object::cast_to<Node>(connection.signal.get_object());
			if (source && !source->is_inside_tree()) {
				continue;
			}
			const StringName method = connection.callable.get_method();
			if (methods_found.has(method)) {
				continue;
			}
			if (!ClassDB::has_method(script->get_instance_base_type(), method)) {
				int line = -1;
				for (int j = 0; j < functions.size(); j++) {
					String name = functions[j].get_slice(":", 0);
					if (name == method) {
						Dictionary line_meta;
						line_meta["type"] = "connection";
						line_meta["method"] = method;
						line = functions[j].get_slice(":", 1).to_int() - 1;
						text_edit->set_line_gutter_metadata(line, connection_gutter, line_meta);
						text_edit->set_line_gutter_icon(line, connection_gutter, get_parent_control()->get_editor_theme_icon(SNAME("Slot")));