Probably closes https://github.com/ppy/osu/issues/35650.
Realm slow, episode 23894. I can't reproduce freezes as big as the video
in the issue is showing but 'realm slow' is 99% the culprit, because
affected user's database is not small.
Takes changes in https://github.com/ppy/osu/pull/34233 and removes *all*
of the complexity.
Supersedes and closes#34233.
Contains same caveat that we can only display one beatmap once in the
carousel; this will be addressed separately.