Fix hiding player controls when playing from media button

DefaultControlDispatcher was removed in ExoPlayer 2.16.0, so the class
extending it that handled play/pause was removed in #8020.

The new solution is to use an instance of ForwardingPlayer. Call
sessionConnector.setPlayer with an instance of ForwardingPlayer that
overrides play() and pause() and calls the callback methods.

Author: ktprograms

app/src/main/java/org/schabi/newpipe/player/helper/MediaSessionManager.java

@@ -13,6 +13,7 @@
 import androidx.annotation.Nullable;
 import androidx.media.session.MediaButtonReceiver;
 
+import com.google.android.exoplayer2.ForwardingPlayer;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.ext.mediasession.MediaSessionConnector;
 
@@ -55,7 +56,17 @@ public MediaSessionManager(@NonNull final Context context,
 
         sessionConnector = new MediaSessionConnector(mediaSession);
         sessionConnector.setQueueNavigator(new PlayQueueNavigator(mediaSession, callback));
-        sessionConnector.setPlayer(player);
+        sessionConnector.setPlayer(new ForwardingPlayer(player) {
+            @Override
+            public void play() {
+                callback.play();
+            }
+
+            @Override
+            public void pause() {
+                callback.pause();
+            }
+        });
     }
 
     @Nullable