### 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)
} else {
			folder_thumbnail = theme_cache.folder_big_thumbnail;
			file_thumbnail = theme_cache.file_big_thumbnail;
		}
		preview_vb->hide();
	} else {
		item_list->set_icon_mode(ItemList::ICON_MODE_LEFT);
		item_list->set_max_columns(1);
		item_list->set_max_text_lines(1);
		item_list->set_fixed_column_width(0);
		item_list->set_fixed_icon_size(Size2());
		if (preview->get_texture().is_valid()) {
			preview_vb->show();
		}
	}
	String cdir = dir_access->get_current_dir();
	dir_access->list_dir_begin();
	List<String> files;
	List<String> dirs;
	String item = dir_access->get_next();
	while (!item.is_empty()) {
		if (item == "." || item == "..") {
			item = dir_access->get_next();
			continue;
		}
		if (show_hidden_files) {
			if (!dir_access->current_is_dir()) {
				files.push_back(item);
			} else {
				dirs.push_back(item);