Do not move focus to top if dim surface is boosted on Task

The activity window on primary container may has a dim effect
showing on the entire task (across the two TFs). In that case,
the activity window should be the visually top-most window.
So do not move focus to the top activity in that case.

Bug: 328167429
Test: atest TaskFragmentTest
Change-Id: I15b13699a50cc59fb9de6793e0ff5191c6d04d08