- Removed online code that didn't work anyway after the introduction of
the development web instance.
- Removed some weird test steps.
- Fixed online/offline test steps not working at all due to identical
user ID.
Was spiritually removed in https://github.com/ppy/osu/pull/16045.
This implementation is mostly taken from that PR's comment thread
verbatim, and now works due to the associated changes to
`OnlinePlayBeatmapAvailabilityTracker`.
The main goal here is to remove the inheritance, since realm doesn't
like that. Unfortunate that we can't use object initialisers in a few of
these places, but no real way around that.