Osu: Playlist option for listening to music while in the main menu

[stageosu]

Describe the new feature: A setting to allow users to select which source of music they want to listen to while on the main menu. The user could, through the options menu, select either "all songs" to shuffle through all songs at random (current functionality), or choose one of their collections to shuffle through.

Proposal designs of the feature:

[stageosu]

I'd like to note while my screenshots are from osu! Stable, the same request applies to Lazer as the interfaces are mostly the same.

[Joehuu]

Should be done here. The functionality in lazer is wrong right now. Should go through songs on current collection like stable, but it is still going through "all beatmaps".

[peppy]

I guess the last selected playlist should be saved, and next song should correctly respect the selected playlist.