Add path to allow task to replace Pipped task without breaking split

* StageCoordinator wasns't handling the case where one of the
splits goes into Pip but doesn't break the split
* We now preemptively guess that an enter transition will
occur when we get the transition that Pip's one of the split tasks
and opens another.
* This is done because Pipping a task out of split results in
2 manual transitions being created in MixedTransitionHelper and
running through StageCoordinator's startAnimation() call again

Bug: 326869501
Test: Repro steps in bug don't break split.
Regular split to pip still works

Change-Id: I2717b1e25d5ac84f77a7a7dc56cee51dcfa08683
(cherry picked from commit 4f9643bc)
Merged-In: I2717b1e25d5ac84f77a7a7dc56cee51dcfa08683