Call removeCallbacksAndMessages() in MediaController#release()

This fixes the NPE ocuured in the MediaControllerImplLegacy#connectToSession()
right after MediaController#release() is called.

libraries/session/src/main/java/androidx/media3/session/MediaController.java

@@ -417,6 +417,7 @@ public class MediaController implements Player {
       return;
       return;
     }
     }
     released = true;
     released = true;
+    applicationHandler.removeCallbacksAndMessages(null);
     try {
     try {
       impl.release();
       impl.release();
     } catch (Exception e) {
     } catch (Exception e) {