### 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)
set_title(TTR("Connections to method:"));
	VBoxContainer *vbc = memnew(VBoxContainer);
	vbc->set_anchor_and_offset(SIDE_LEFT, Control::ANCHOR_BEGIN, 8 * EDSCALE);
	vbc->set_anchor_and_offset(SIDE_TOP, Control::ANCHOR_BEGIN, 8 * EDSCALE);
	vbc->set_anchor_and_offset(SIDE_RIGHT, Control::ANCHOR_END, -8 * EDSCALE);
	vbc->set_anchor_and_offset(SIDE_BOTTOM, Control::ANCHOR_END, -8 * EDSCALE);
	add_child(vbc);
	method = memnew(Label);
	method->set_horizontal_alignment(HORIZONTAL_ALIGNMENT_CENTER);
	vbc->add_child(method);
	tree = memnew(Tree);
	tree->set_columns(3);
	tree->set_hide_root(true);
	tree->set_column_titles_visible(true);
	tree->set_column_title(0, TTR("Source"));
	tree->set_column_title(1, TTR("Signal"));
	tree->set_column_title(2, TTR("Target"));
	vbc->add_child(tree);
	tree->set_v_size_flags(Control::SIZE_EXPAND_FILL);
	tree->set_allow_rmb_select(true);
}
Vector<String> ScriptTextEditor::get_functions() {