Prefer the launch display to the source when looking for task/stack

When launching an activity with a launchDisplayId, look for affinity
matches on that display or use the focused stack when it is on that
display (instead of using the source display).

Test: android.server.cts.ActivityManagerDisplayTests
Test: #testLaunchDisplayAffinityMatch
Bug: 38502844
Change-Id: I2ddf00e3107a8188aaf88553aedc5802e2d251bf