It could potentially never fade in on quick presses.
- Add a download failed event to BeatmapManager - Make DownloadButton aware of all 3 possible download states - Change button appearance based on each state
Allows progressing forwards in the interface
# Conflicts: # osu.Game/Screens/Select/FilterControl.cs
Use IMouseWheelBindingHandler for volume VolumeControlReceptor. VolumeMeter is no longer an IKeyBindingHandler because it is unused.
Add a default ruleset to `OsuTestCase` to cover testing scenarios.
Also decouples the bindable at SongSelect, where it is debounced in line with the carousel being updated.