Proper Now Playing and PiP support

[ktprograms]

Now Playing and improved player seek code from https://developer.apple.com/documentation/mediaplayer/becoming_a_now_playable_app/

• Use lazyPlayer for data to put in Now Playing.
• Observe playback rate and playback status and update in Now Playing data.
• Add Playback Rate, Skip Backward, Skip Forward and Playback Position commands to Now Playing.
• Setup now playing controls when playback starts (instead of when going to background).
• Add setting to configure whether playback changes to Audio Only or Picture in Picture when app goes to background. Note: PiP sometimes doesn't automatically start when backgrounding from split view. This seems to be related to the scene width, and it also happens with other apps (the Apple Developer app).
• Only disconnect player when scene enters background. This keeps video visible while in the app switcher, or changing width in split view.
• Stop Now Playing, External controls and AirPlay when closing mini player in-app.

Fix: #226 Fix: #338

[ktprograms]

Diff 7c812ba...aa8b644: Fix Lint errors

[anohren]

Looking forward to trying this out later!

[anohren]

Nice work!

There are still a few quirks on iOS 15.5 but it's possible to watch in PiP now