Fix daily challenge not querying beatmap properly
Rewrite playlists to not inherit `RoomSubScreen`
Fix playlists results screens potentially displaying negative score positions
RoomsContainer
Create, join, and part multiplayer rooms only via the multiplayer server
Somewhat informal because it isn't super easy to handle.
SelectedRoom
OnlinePlayTestScene
I believe once upon a time the `SelectedRoom` bindable used to be bound to `RoomManager.JoinedRoom` or similar. But now it's effectively private to the lounge subscreen and so a lease is unnecessary.
RoomManager
As we're moving towards using the `/playlist/<id>/scores/<id>` endpoint, the existing playlists results screen classes needed some restructuring.
Room.Playlist
Room.RecentParticipants
Room.MaxAttempts
Room.Duration
Room.StartDate
Room.EndDate
Room.ParticipantCount
Room.MaxParticipants
Room.Host
Room.Name
Most important changes are to `RoomSubScreen` and `PlaylistsRoomSubScreen`, because those are the only two cases that now bind to the event instead.