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
diff --git a/services/core/java/com/android/server/wm/TaskDisplayArea.java b/services/core/java/com/android/server/wm/TaskDisplayArea.java
index 13e4d8b..d7896c7 100644
--- a/services/core/java/com/android/server/wm/TaskDisplayArea.java
+++ b/services/core/java/com/android/server/wm/TaskDisplayArea.java
@@ -1603,6 +1603,11 @@
         }
     }
 
+    @Override
+    boolean canCreateRemoteAnimationTarget() {
+        return true;
+    }
+
     /**
      * Callback for when the order of the stacks in the display changes.
      */