Check for leftTopTask and rightBottomTask in KQS.

KQS currently always take the GroupTask's taskId1 and taskId2 as
leftTop/rightBottom, in that order. However, sometimes it is possible
that the order is flipped; RecentTasksController#getRecentTasks return a
list of tasks base on recency, and it is possible that when it
initializes a new GroupTask, it put leftBottom as task2 and vice versa,
completely dependent on how they are processed. This CL uses
GroupTask#mSplitBounds as the source of truth to see

1) Which leftTop/rightBottom to draw for the thumbnail and
2) Which task is leftTop, which task is rightBottom, for re-launching

Bug: 328691131
Test: Manually; using KQS, no longer see the app in the wrong places
Flag: EXEMPT bugfix
Change-Id: I14b3becb05359a917372ec2d7d80d32190f0f96b