Return resume result in resumeFocusedStacksTopActivities

The method addToFinishingAndWaitForIdle cannot know the next home
was successful resume because the last result of
resumeTopActivityUncheckedLocked was not returned, so FallbackHome
can be destroy immediately without waiting for next home activity
to be idle.

Add test testCompleteFinishing_lastActivityAboveEmptyHomeStack

Bug: 143199498
Test: atest ActivityRecordTests
Test: atest MultiDisplaySystemDecorationTests ActivityVisibilityTests
SplitScreenTests PinnedStackTests
Change-Id: Icbe436afd66d2c2e5a9b884433e2fea84c119513