API for moving top activity in a stack to pinned stack.

* AMS.moveTopStackActivityToPinnedStack can be used to move the top
activity in a stack to the pinned stack and also specify the bounds
the pinned stack should be sized to.
* 'am stack move-top-activity-to-pinned-stack' command for testing
AMS.moveTopStackActivityToPinnedStack API

Bug: 25006507
Change-Id: I8392b4c39d8542153e691be7a627b7f35fd44884