Animate divider bar and roottasks along with keyguard-exit

This fixes some bugs along the way too.
1. task snapshot matrix excludes translation. Before it was included
   causing a double-offset.
2. Stack-clip-mode is NONE for keyguard transits now (probably should
   always be none).

There is also some changes to hierarchy transition. Specifically:
1. Raised promotable containers up to TaskContainer level
2. Moved leash reposition (to 0,0) up to windowcontainer

Bug: 148906453
Test: Enter split-screen, lock then unlock device.
Change-Id: I7f09585b43790586d4bbed7b296c0373df6d60c3