Improve enter split transition

Improve enter split transition by two part changes.
1. Enter split with resizing animation:
   We directly show split but no animation before, it might looks
   bad to user because UI change too many things in few frames.

2. Fix flicker cause by black screen when split active:
   When we start intent on side stage task, the top split root task
   will go to top and current top one task will be set as invisible
   then cause black screen due to split root task is full screen.
   Solve this by use new wct api setForceTranslucent to make split
   root task as translucent when split inactive. We need to reset
   it when split active otherwise it cause flicker when back to home.

   Except above change, we also need to set side stage bounds to
   area outside of screen otherwise it still cause flicker because it
   will show a flash of shadow when launch intent on side stage.

   This solution should be removed after shell transition fully
   landing because in shell transition we could make those transitions
   be done in one transition.

Bug: 223325631
Test: manual
Test: pass existing tests
Change-Id: Iabc6ad708df021895783003d6267a7ed5dbc6d38