Keep task hidden until task appeared

- If the task is previously not visible or has no visible children at
  the point when we start controlling it in the task org, hide the task
  until we send taskAppeared to ensure that the task org can reparent
  and show it otherwise we could see a flash of the task.

  This happens mainly from two cases:
  - when starting a new task with a given win mode, we show it and wait
    for first draw before notifying the task org
  - when transitioning into pip from swipe up, the activity is hidden
    and when it requests to enter pip is made visible again

  Since we are hiding the task w/ the pending transaction, we also need
  to defer all task org callbacks until that's applied to ensure proper
  lifecycle of the calls.
- Also skip app transitions for task org tasks for now

Bug: 152809695
Bug: 152134460
Test: Open a bubble, ensure that we don't see the task in fullscreen
      first.  Enter pip, ensure that we don't see flash of the task
      before SysUI can fade it in.
Test: atest PipAnimationControllerTest
Test: atest TaskOrganizerTests
Test: atest SplitScreenTests

Change-Id: If51e98cd007faef35e99acd31b27b20eebbea010