Revert "Revert "Fix resize info activity not showing in some cases""

This reverts commit 25cbe9d7.

Fix resize info activity not showing in some cases

Show all visible activities in split screen primary window.
Add test to verify showing all activities.

Reason for revert: Adding back chagnes to fix original bug.
Seems that the changes in the original CL uncovered a different bug.

Bug: 156314330
Bug: 135520403
Test: atest CtsWindowManagerDeviceTestCases:PinnedStackTests
      atest WmTests:ActivityStarterTests

Change-Id: I547e546708b669e055b9b9d9957c53bea50e52a6