Handle intermediate task overlay for metrics logger

The corner case is introduced by intercepting trampoline
activity launch with launching task overlay.
E.g. trampoline -> permission prompt -> main -> permission prompt
Because the prompt is overlay, there may not have visibility
change. The first prompt may be cancelled by consecutive launch
too earlier. And the second prompt which finishes immediately
may miss to cancel.

Bug: 222576471
Test: ActivityMetricsLaunchObserverTests# \
      testOnActivityLaunchCancelled_finishedBeforeDrawn
Change-Id: Ife39b7238169a1d54f3d60d1655868cc3cb73f25