ErrorProne: AudioUtil

remove unused code + implement a few hasCode for
(MediaData|MediaController|Metadata|Image)

MediaPlayerList:
```
734: warning: Conversion from long to float may lose precision;
  use an explicit cast to float if this was intentional
                    .setState(PlaybackState.STATE_STOPPED, 0L, 0L);
                                                               ^
842: warning: MediaSession.Token is final and does not override Object.toString,
                                + token);
                                  ^
```

MediaPlayerWrapper:
```
xxx: warning: This access should be guarded by 'this.mCallbackLock', which is not currently held
        mControllerCallbacks = new MediaControllerListener(mMediaController, mLooper);
        ^
309: warning: Comparison using reference equality instead of value equality
        if (newController == mMediaController) return;
                          ^
456: warning: Calling equals on incompatible types MediaMetadata and Metadata
            if (Objects.equals(metadata, mCurrentData.metadata)) {
                              ^
```

BTAudioEventLogger.java:
```
32: warning: Inner class is non-static but does not reference enclosing class
    private class Event {
            ^
```
BrowsedPlayerWrapper:
42: warning: Log tag too long, cannot exceed 23 characters.
    private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
                                                        ^
```
AvrcpPassthrough:
```
120: warning: Switch case has 'fall through' comment, but execution cannot fall through from the previous case
            case BluetoothAvrcp.PASSTHROUGH_ID_SELECT:
            ^
```

Bug: 236759221
Test: m RUN_ERROR_PRONE=true Bluetooth
Change-Id: Ie5c4c37cc16508028f9519bda42da30135b04078