Decouple external video playback from internal playback code

[nielsvanvelzen]

This is an older branch and I'm not entirely sure what I didn't finish 🙈. Needs testing (@BotBlake, @TimGels). I need this for a different change I'm working on, that is needed for yet another change I want to work on 🗿.

Changes

• Rewrite ExternalPlayerActivity
  • Detached from other playback code (except for the queue)
  • Cleaner code, removed a bunch of cruft
  • always directplays the file

Testing needed for:

• Do all subtitles still work (including external?)
• Does reporting still work (e.g. is the item marked watched when returning to the app)
  • Does reporting also not work when the external player fails to play?
• Does the queue advancing still work? (auto play next item on finish)

Issues

[TimGels]

@nielsvanvelzen which external player needs to be tested? I have a few that I can test like vlc and mx player.

[nielsvanvelzen]

Just in general to see if the Jellyfin app still behaves like it should, you can test that with whatever external player you want.

[theguymadmax]

Resume from x position - starts playback at the start for both Just Player and VLC
Just Player - will save the resume position
VLC - doesn't save the resume position

External subs don't display as an option for Just Player (use to)
External subs don't display as an option for VLC (never did)

[BotBlake]

From playing arround a bit, I didnt find direct Playback Issues.
(Tested on CCwGTV HD using MXPlayer)

All issues I found:

• autoplay of the next Episode does not work.

• VLC support is back? - Using VLC as external player not working on stable but on this branch

• On Some files AC3 Audio doesnt play (MXPlayer) (also an issue on stable)

• Client Ignores External Player Setting when using Playlist (also an issue on stable)

• Shuffle all episodes completely breaks Seeking (MxPlayer) (also an issue on stable)

• I forgot what I wanted to write because I fell asleep (a me issue)

• Integrated Subs dont show on MXPlayer (also an issue on stable)