Introduce CLI frontend rewrite based on Click

[JOJ0]

• The new main command is named dsc and might be renamed later.
• The argparse based command disco is still available for reference.
• ctrls.py code is kept as-is, only the cli frontend and the args helper was redesigned.
• Fixed some bugs on the way, that existed with disco already.
• TestBrainz suite disabled in CI, it fails when run via gh-actions.

Issues:

• Docs are not updated yet.
• Tested a lot but not too thorougly.