Lazy TUI Playlist

[hasezoey]

This PR makes the TUI Playlist lazy loading.

Currently known limitations:

• Playlist Total Duration had to be disabled (as we now not have access to all of the durations at load)
  • i intend to fix this in a future PR which implements the lazy playlist serverside and the TUI can load this info via protobuf
• Playlist Search is very slow (as it has to load all the playlist data, as before, just it is now the only all consumer)
  • i intend to fix this by allowing search on the id (path / url) while loading the data, and even after it is loaded allow to search on the id, but at a lower weight

I would appreciate some additional testing before this is being merged.

Notes about the implementation:

• anything that requires access to the current track's information, either will:
  • load the info on next redraw (playlist), or
  • has to be manually told to re-load its data (update_photo, lyric_title, "Currently Playing" message)
• the track info loader (TMPTrackLoadMsg) is a temporary helper actor until the info can be loaded from the server via protobuf

Depends on #784
re #493

Tagging @Porkepix in case you are interested to test this change.