### Godot version

4.1.1

### System information

linux

### Issue description

- When favoriting a path in a `FileDialog`, clicking on it travels to `path/to/dir/`.
- When going up a level from there, it doesn't go to `path/to` but to `path/to/dir` (without the `/`).

[simplescreenrecorder-2023-08-18_09.38.37.webm](https://github.com/godotengine/godot/assets/71937306/00c20ad3-292f-4961-84ed-dbc64906df52)

The problem is either (or both) that:
 - loaded path has a trailing `/`
 - parent dir of `stuff/` is considered to be `stuff`

### Steps to reproduce

favorite a directory and use the feature to navigate to it

### Minimal reproduction project

any (i.e. the project manager's "new project" dialog has one)
int thumbnail_size = EDITOR_GET("filesystem/file_dialog/thumbnail_size");
	thumbnail_size *= EDSCALE;
	Ref<Texture2D> folder_thumbnail;
	Ref<Texture2D> file_thumbnail;
	item_list->clear();
	
	item_list->get_v_scroll_bar()->set_value(0);
	if (display_mode == DISPLAY_THUMBNAILS) {
		item_list->set_max_columns(0);
		item_list->set_icon_mode(ItemList::ICON_MODE_TOP);
		item_list->set_fixed_column_width(thumbnail_size * 3 / 2);
		item_list->set_max_text_lines(2);
		item_list->set_text_overrun_behavior(TextServer::OVERRUN_TRIM_ELLIPSIS);
		item_list->set_fixed_icon_size(Size2(thumbnail_size, thumbnail_size));
		if (thumbnail_size < 64) {
			folder_thumbnail = theme_cache.folder_medium_thumbnail;
			file_thumbnail = theme_cache.file_medium_thumbnail;