Find task on preferred display first

It is possible to have more than one reusable tasks in
multi-display scenario. We should always look up the best
task on the preferred display prior to other displays.

Bug: 71495111
Test: atest ActivityManagerMultiDisplayTests
      atest FrameworksServicesTests:com.android.server.am.ActivityStackTests

Change-Id: I9e78912f820b143bdd7eae5a770e86549d8b298a