2/ Add API to start overview activity with assist callbacks

- Only the recents component package can launch the overview activity
  directly, and if an assist data receiver is provided, then assist data
  will be proxied to the caller.

Bug: 67864419
Test: com.android.server.am.RecentTasksTest
Test: com.android.server.am.AssistDataRequesterTest
Test: CtsVoiceInteractionTestCases
Change-Id: Icdd7e6716a84c11e9262ce5453f7d39ae7d8ce77