Fix janky animation when enter pip from secondary split

This happens to both Activity Embedding split and system split screen.

Two issues to fix:
1. When entering, the pip activity surface is first jump to the left.
   This is because the start bounds of the pip Task is not set to the
   bounds of the activity original bounds (reset because of fullscreen
   mode).
2. When animating the pip content overlay on top, it only covers partial
   of the pip surface. This is because the bounds of the secondary split
   has an offset, so when animating, the postScale is not using the
   correct center.

Fix: 306994352
Test: atest FlickerTestsOther:SecondaryActivityEnterPipTest
Change-Id: I567efd7ed52d91ec49eb4adee81a8cb7a6381ade