### Godot version

4.0.3.stable

### System information

windows 11

### Issue description

fullscreen on the window node is not working and will show up as a windowed.

### Steps to reproduce

disable Embed Subwindows in Project Settings/Display/Window.
create a window node and set its mode to fullscreen.

### Minimal reproduction project

[fullscreen.zip](https://github.com/godotengine/godot/files/11821834/fullscreen.zip)
ERR_MAIN_THREAD_GUARD;
	switch (p_what) {
		case NOTIFICATION_POSTINITIALIZE: {
			initialized = true;
			_invalidate_theme_cache();
			_update_theme_item_cache();
		} break;
		case NOTIFICATION_PARENTED: {
			theme_owner->assign_theme_on_parented(this);
		} break;
		case NOTIFICATION_UNPARENTED: {
			theme_owner->clear_theme_on_unparented(this);
		} break;
		case NOTIFICATION_ENTER_TREE: {
			bool embedded = false;
			{
				embedder = get_embedder();
				if (embedder) {
					embedded = true;
					if (!visible) {
						embedder = nullptr; 
					}
				}
			}
			if (embedded) {