When the Qt QPA closes it deletes the wl_display
deleting wl_display deletes the wl_registry
when we destroy the kwayland wrapper we double delete
as the windowsystem integration is a singleton we're not deleted till
after qApp.
By manually releasing the wayland parts early we avoid that problem,
whilst still being safe if any app did make a KWindowSystem call during
shutdown.
BUG: 374665