Major Events Overhaul

Special thanks to @eladyn for all of their help and suggestions.

* Add all player events to `player_event_handler.rs`

* Move event handler code to `player_event_handler.rs`

* Add session events

* Clean up and de-noise events and event firing

* Added metadata support via a TrackChanged event

* Add `event_handler_example.py`

* Handle invalid track start positions by just starting the track from the beginning

* Add repeat support to `spirc.rs`

* Add `disconnect`, `set_position_ms` and `set_volume` to `spirc.rs`

* Set `PlayStatus` to the correct value when Player is loading to avoid blanking out the controls when `self.play_status` is `LoadingPlay` or `LoadingPause` in `spirc.rs`

* Handle attempts to play local files better by basically ignoring attempts to load them in `handle_remote_update` in `spirc.rs`

* Add an event worker thread that runs async to the main thread(s) but sync to itself to prevent potential data races for event consumers.

* Get rid of (probably harmless) `.unwrap()` in `main.rs`

* Ensure that events are emited in a logical order and at logical times

* Handle invalid and disappearing devices better

* Ignore SpircCommands unless we're active with the exception of ShutDown

examples/play.rs

@@ -36,7 +36,7 @@ async fn main() {
         exit(1);
     }
 
-    let (mut player, _) = Player::new(player_config, session, Box::new(NoOpVolume), move || {
+    let mut player = Player::new(player_config, session, Box::new(NoOpVolume), move || {
         backend(None, audio_format)
     });