Steps to remove PouchDB-Server from PouchDB

[SourceR85]

We started to drop PouchDB-Server from PouchDB.

Here are some ToDo's from #8948 that immediately came to mind:

• Communicate the deprecation of PouchDB-Server clearly in the release notes!
• remove or mark it as outdated in TESTING.md
• update coverage script in package.json (uses pouchdb-server)
• remove pouchdb-setup from bin/run-test.sh

Feel free to left your thoughts, if I've missed something here.