Fix recents thumbnail wrong while swipe up

This bug occured when it has multiple visible app targets need to
show. If surface didn't have specific layer, their display order
will be determined by create timing. By such rule, we should create
their animation leash by down to top rather than top to down.

This patch also fix wrong logic to create RecentsAnimationSplitTasks,
we should only do that when split is active.

Fix: 223396876
Fix: 207390696
Test: manual
Test: pass existing tests
Change-Id: I74a33cdc28d370f1db3910ebda8577c72416bc97