### 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)
pathhb->add_child(l);
	drives_container = memnew(HBoxContainer);
	pathhb->add_child(drives_container);
	dir = memnew(LineEdit);
	dir->set_structured_text_bidi_override(TextServer::STRUCTURED_TEXT_FILE);
	pathhb->add_child(dir);
	dir->set_h_size_flags(Control::SIZE_EXPAND_FILL);
	refresh = memnew(Button);
	refresh->set_flat(true);
	refresh->set_tooltip_text(TTR("Refresh files."));
	refresh->connect("pressed", callable_mp(this, &EditorFileDialog::update_file_list));
	pathhb->add_child(refresh);
	favorite = memnew(Button);
	favorite->set_flat(true);
	favorite->set_toggle_mode(true);
	favorite->set_tooltip_text(TTR("(Un)favorite current folder."));
	favorite->connect("pressed", callable_mp(this, &EditorFileDialog::_favorite_pressed));
	pathhb->add_child(favorite);
	show_hidden = memnew(Button);
	show_hidden->set_flat(true);
	show_hidden->set_toggle_mode(true);
	show_hidden->set_pressed(is_showing_hidden_files());
	show_hidden->set_tooltip_text(TTR("Toggle the visibility of hidden files."));
	show_hidden->connect("toggled", callable_mp(this, &EditorFileDialog::set_show_hidden_files));
	pathhb->add_child(show_hidden);
	pathhb->add_child(memnew(VSeparator));
	Ref<ButtonGroup> view_mode_group;
	view_mode_group.instantiate();
	mode_thumbnails = memnew(Button);
	mode_thumbnails->set_flat(true);