Allow resize for secondary split screen

We use to resize the stack whenever there is new override bounds and
accidentally make that for primary split screen only in ag/9720001

Bug: 146879048
Test: atest PinnedStackTests
Test: atest ActivityLifecyclePipTests.testSplitScreenBelowPip
Test: atest ActivityLifecycleSplitScreenTests.testResumedWhenRecreatedFromInNonFocusedStack
Test: atest ActivityLifecycleSplitScreenTests.testOccludingMovedBetweenStacks

Change-Id: If9cfe76c79e054cc10288ae3b955478e80a2ce92