(suggested by peppy)
Allows for better testability.
# Conflicts: # osu.Game/Screens/Select/SongSelect.cs
# Conflicts: # osu.Game/Screens/Select/FilterControl.cs
Add a default ruleset to `OsuTestCase` to cover testing scenarios.
Already logged to network.log with ample detail.
Also decouples the bindable at SongSelect, where it is debounced in line with the carousel being updated.