session: fix IllegalStateException when calling setSessionExtras()

...from thread which isn't application thread. This change makes the
demo app work with player using a non-main application thread.

Author: nift4

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

@@ -1135,7 +1135,7 @@ public void onSessionExtrasChanged(int seq, Bundle sessionExtras) {
       PlayerWrapper playerWrapper = sessionImpl.getPlayerWrapper();
       playerWrapper.setLegacyExtras(sessionExtras);
       sessionCompat.setExtras(playerWrapper.getLegacyExtras());
-      sessionCompat.setPlaybackState(sessionImpl.getPlayerWrapper().createPlaybackStateCompat());
+      updateLegacySessionPlaybackState(sessionImpl.getPlayerWrapper());
     }
 
     @Override