Allow different tab tearing transitions.

Updates tab tear to allow fullscreen and split-snap. Also updates
the default case to start the new activity at the position of the drop,
rather than the default determined by the system and cascading logic.

Note that the above freeform cases rely on any trampoline activities
setting the Window_windowNoDisplay attribute so that the child Intent
may inherit startingBounds until another method of detecting trampoline
activities is implemented.

Video: http://recall/-/d6fa8QQfzERZDRGCuQib4/fkt4rPvvoc5cq6JW31exYl
Bug: 356263495
Test: manual
Flag: EXEMPT bugfix
Change-Id: I70e8fe5015aad81f5b4412e6fb58feeda84fdb0c