### 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)
CodeEdit *text_edit = code_editor->get_text_editor();
	Color updated_marked_line_color = EDITOR_GET("text_editor/theme/highlighting/mark_color");
	Color updated_safe_line_number_color = EDITOR_GET("text_editor/theme/highlighting/safe_line_number_color");
	Color updated_folded_code_region_color = EDITOR_GET("text_editor/theme/highlighting/folded_code_region_color");
	bool safe_line_number_color_updated = updated_safe_line_number_color != safe_line_number_color;
	bool marked_line_color_updated = updated_marked_line_color != marked_line_color;
	bool folded_code_region_color_updated = updated_folded_code_region_color != folded_code_region_color;
	if (safe_line_number_color_updated || marked_line_color_updated || folded_code_region_color_updated) {
		safe_line_number_color = updated_safe_line_number_color;
		for (int i = 0; i < text_edit->get_line_count(); i++) {
			if (marked_line_color_updated && text_edit->get_line_background_color(i) == marked_line_color) {
				text_edit->set_line_background_color(i, updated_marked_line_color);
			}
			if (safe_line_number_color_updated && text_edit->get_line_gutter_item_color(i, line_number_gutter) != default_line_number_color) {
				text_edit->set_line_gutter_item_color(i, line_number_gutter, safe_line_number_color);
			}
			if (folded_code_region_color_updated && text_edit->get_line_background_color(i) == folded_code_region_color) {
				text_edit->set_line_background_color(i, updated_folded_code_region_color);
			}
		}
		marked_line_color = updated_marked_line_color;
		folded_code_region_color = updated_folded_code_region_color;
	}
	theme_loaded = true;
	if (!script.is_null()) {
		_set_theme_for_script();
	}
}
void ScriptTextEditor::_set_theme_for_script() {