Allowing tap outside focus changes for pre-Q non-top window

For compatibility reasons, non-top app windows that target earlier
SDK may not have focus if there has another window that is higher
and has focus. In that case, we were unable to switch focus to the
window since it cannot handle tap outside events.

Also remove #ensureActivitiesVisible while handling focus change,
since it is no longer necessary.

Bug: 123761773
Test: atest MultiDisplayPolicyTests
Change-Id: I5afac910ecb4806dc190b37f1dccd4cba4d76f9f