Do map rotation via script

[Alystrasz]

Currently, when server fetches maps resource of the API, it assumes there is one map configuration per map entry in its playlists_v2.txt file; this prevents a map from featuring multiple configurations.

We could allow that by letting server do the map rotation itself instead of depending on playlists_v2.txt.

Example mod doing map rotation: https://thunderstore.io/c/northstar/p/Maxb0tbeep/MapSelect/

[Alystrasz]

Since 054ec10, server is able to round-robin over existing map configurations; technically, it selects the next map excluding the ones previously played, but the same logic can be reused with map configurations.
Closing for now.