Remove MediaSessionEngine

Bug: 128970771
Test: atest CtsMediaTestCases:android.media.cts.MediaSessionTest;
      atest CtsMediaTestCases:android.media.cts.MediaControllerTest;
      atest CtsMediaTestCases:android.media.cts.MediaBrowserTest;
      atest CtsMediaTestCases:android.media.cts.MediaSessionManagerTest;
Change-Id: I7276de966b17b4b5c806e2b9c5ac5e4646e2fd07
3 files changed