Optimize App -> Recents

- Use same strategy to draw thumbnail bitmap by moving
startActivity off from the main thread and start caching the future
when AM is busy executing startActivity.
- Move some binder calls off the main thread.
- Add some trace points for better analysis in the future.
- Make toggleRecentApps asynchronous so we don't have to wait on
the next app-vsync - it's totally not needed.

Test: com.android.apptransition.tests.LatencyTests

Change-Id: I15db41f2e821779972ab3b430033c70aa1dfd907
Fixes: 32668632