When not using previews, we currently use a numerical presentation like "1 / 4" for the top bar button. We will change that to use the active workspace name instead. As the menu already has to track workspace switches and name changes, expose the active workspace name there, so that the button doesn't have to duplicate the tracking. Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/405>