Stop or destroy activities when all resumed activities are shown

So the stopping activities won't be delayed too long if the resumed
activity doesn't report idle.

Bug: 130340090
Test: atest ActivityVisibilityTests# \
            testActivityStoppedWhileNextActivityNotIdle
            testNoHistoryActivityFinishedResumedActivityNotIdle

Change-Id: Ia161456b6d3e5eb68184c429df3b6bed24d0683e