[Feature Request] Personal playlist with alternating play depending on users in channel

**Is your feature request related to a problem? Please describe.**
People like to argue about which songs should be played.

**Describe the solution you'd like**
Every user has his personal playlist, if nothing else is queued the autoplaylist is populated by songs on personal playlists in alternating order of all users in the respective voice channel.
If for example two users are currently connected to the voice channel, it will play a random song on user A's personal playlist, after that, play a song of user B's personal playlist.

**Describe the basic flow/steps of using this feature**
How this feature would be used:
1. I use a command to add songs to my personal playlist
2. I join a music voice channel
3. The bot plays random songs of my personal playlist
4. Another user joins; the user also has a personal playlist
5. The bot fairly alternates between both personal playlists
6. A song is requested
7. The next song played, will be the requested song
8. As soon as the queue is finished, it resumes playing songs from personal playlists

**Have you confirmed that this idea is not already described here?**
Yes

The issue names no files or tests. Begin by locating the existing personal-playlist command, voice-channel queue or autoplaylist handling, and requested-song flow, then compare them with the numbered usage steps. Done means personal playlists alternate fairly among users in a voice channel, requested songs take priority, and autoplay resumes after the queue ends.

Written by the indexing model from the issue text.