Also rename GetBackground to CreateBackground, since it's returning a new instance.
Update framework with ICollection & IReadOnlyList Containers
Update sorting comparers in line with framework changes
Remove assert which is not always true on some operating systems
Fix osu! logo on main menu ending up in the wrong place
Also switch to using BeginDelayedSequence where possible.
No longer required as mono 5.0 upwards handles this gracefully (while not yet adding full parallel support).
Update framework
Update transform usage in line with framework changes
TestCase for BeatSyncedContainer