PIP: Start consulting TaskOrganizer for bounds instead of framework.

SysteUI now owns the PIP surface and its movement, etc, and should be
the source of truth for MotionHelper to ask for current PIP bounds. We
can then avoid making a call to framework to query this.

Bug: 153369299
Test: atest PinnedStackTests
Change-Id: If614a1cefb4b28ad7177ad6569371e5aa077153d