Verify that TaskOrganizer gets transferred launch cookie

If task A launches task B before A is drawn, the launch cookie
will be transferred from A to B. So onTaskAppeared should only
get the launch cookie from B.

Also clean up duplicated usages of ITaskOrganizer in unit tests.

Bug: 129067201
Test: atest WmTests:ActivityOptionsTest#testTransferLaunchCookie
Change-Id: I63bc8cd339642d3131c6a666cfffe37ad1a4c611