Before attempting to fix issues with invalid selections reaching
gameplay, I needed to do a pass of the song select class as selection
logic was already more complex than I'd hope.
All operations now go through a single flow (`SelectAndRun`) when
leaving the song select screen in a "success" state.
Closes https://github.com/ppy/osu/issues/33336.
I was worried that doing that was going to cause terminal breakage but
in testing it does not appear to so I'm just going to do this and call
it a day.