[WIP/RFT] Remove usage of window type META_WINDOW_OVERRIDE_OTHER

This removes the usage of the window type META_WINDOW_OVERRIDE_OTHER. It was in the way when deciding which windows have to go into top_window_group.
For ABI/API-stability, I'm leaving the actual type in the code, including the references in switch-case (to prevent compiler warnings). it doesn't hurt, because the type is not actually assigned to any window.

This also adds META_WINDOW_MENU and META_WINDOW_UTILITY to top_window_group.

This goes together with linuxmint/Cinnamon#2257.