### 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 (!p_path.size()) {
		return;
	}
	int pos = MAX(p_path.rfind("/"), p_path.rfind("\\"));
	if (pos == -1) {
		set_current_file(p_path);
	} else {
		String path_dir = p_path.substr(0, pos);
		String path_file = p_path.substr(pos + 1, p_path.length());
		set_current_dir(path_dir);
		set_current_file(path_file);
	}
}
void EditorFileDialog::set_file_mode(FileMode p_mode) {
	mode = p_mode;
	switch (mode) {
		case FILE_MODE_OPEN_FILE:
			set_ok_button_text(TTR("Open"));
			set_title(TTR("Open a File"));
			can_create_dir = false;
			break;
		case FILE_MODE_OPEN_FILES:
			set_ok_button_text(TTR("Open"));
			set_title(TTR("Open File(s)"));