od-unix: preserve Qt runtime config on restart

od-unix: preserve Qt runtime config on restart

The Qt runtime launcher applied settings only for start/reset actions
and dropped the temporary config snapshot before calling uae_restart().
That made the restarted process seed the launcher from default.uae
instead of the config that the user had just accepted.

Apply launcher settings for restart requests too, keep the runtime
snapshot alive across uae_restart(), and teach startup to seed the Qt
launcher from the loaded config when one is available. Remove the
temporary snapshot after the restarted frontend has consumed it.