Add a check for the working beatmap background width and assign a proper scaling value to cover the whole box
Fix wrong initial state of beatmap panels.
# Conflicts: # osu.Desktop.VisualTests/Tests/TestCasePlayer.cs # osu.Game/Beatmaps/Objects/Osu/Drawable/DrawableCircle.cs
# Conflicts: # osu-framework
# Conflicts: # osu.Game/Beatmaps/Drawable/Panel.cs