language: Wait for locale generation before offering a logout
If a user chooses a locale that's not generated yet, selecting it will trigger locale generation. This can take a while, but happens in the background and isn't indicated in any way, so if the user presses the logout button they won't get the newly selected locale in effect because it won't be generated yet. The UI should tell the user to wait until the generation is done.
Related: pureos/core/gnome-initial-setup#5