Basically, `BeatmapCarousel.CurrentSelection`, which is
magic-object-typed, can no longer use `BeatmapInfo` directly, it now
must also use `GroupedBeatmap`.
This spills out all the way into song select because of beatmap
selection flows that require hookup from song select.
Previously, random selection would always be done at a *set* level. The
final operation of a random action would be "select the user's
recommended difficulty from this randomly selected set".
This makes no sense when sets are not grouped together at song select.
In fact, it is completely broken with the previous commit which adds
group-isolated random support – if we're grouping by difficulty and the
user's recommendation is not in the current group it would throw the
user into another group unexpectedly.
This fixes the issue by splitting out the random implementation into two
separate pathways depending on the carousel display mode.
This is a minimal implementation in order to keep moving forward.
For simplicity I've copied over the old implementation verbatim. Note
that this is beatmap*set* based randomisation, which means that when
panels are split up by difficulty, it is still randomising by set (with
the difficulty choice being left up to the user recommendation system).
I think this is what we want, but if it isn't, any changes can come
later.
This isn't strictly required, but there should be no gaurantee or
requirement that the references are equal in these checks, so it's best
change them as such.
This aims to bring some conformity to naming to make it easier to
understand component structure for new components.
Renames are pulled out of the song select v2 changes and are more
relevant there due to many new classes being added.
- `V2` suffix is dropped, with v2 components being moved to a relevant V2 namespace.
- Related classes have a prefix of the area they are used.
- Experimenting with using partial/nested classes in the song select v2 implementation.
Not committing to this yet but want to see how it plays out.
- Moved base carousel components to a generic namespace to avoid confusion with actual beatmap carousel implementation.