### 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)
if (display_mode == DISPLAY_LIST || p_preview.is_null()) {
		return;
	}
	for (int i = 0; i < item_list->get_item_count(); i++) {
		Dictionary d = item_list->get_item_metadata(i);
		String pname = d["path"];
		if (pname == p_path) {
			item_list->set_item_icon(i, p_preview);
			item_list->set_item_tag_icon(i, Ref<Texture2D>());
		}
	}
}
void EditorFileDialog::_thumbnail_done(const String &p_path, const Ref<Texture2D> &p_preview, const Ref<Texture2D> &p_small_preview, const Variant &p_udata) {