Handle stopping and finishing activities on drawn

If the non idle activity is started in a new task, there may have
a starting window. So the transition animation can be done with
the starting window but the main window of the activity may not
finish drawing if it is slow during startup. That causes the
allResumedActivitiesVisible to return false and the stopping
activities are still pending.

By scheduling to process stopping and finishing when the activity
windows are actually drawn (though its name is onWindowsVisible,
it is only called if the windows are drawn, see numVisible), the
pending stopping activities no longer need to wait until idle timeout
to be stopped or destroyed.

Also avoid sending duplicated idle message.

Bug: 169740664
Test: atest ActivityVisibilityTests# \
      testActivityStoppedWhileNextActivityNotIdle
Change-Id: I7317bf577a1b98601b6ec027a5d7bf66090aecde