Move RecyclerView scroll capture to the center

Avoid most floating content by centering the requested content within
the view instead of just scrolling so that it's visible.

Bug: 174571735
Test: atest RecyclerViewCaptureHelperTest, plus manual testing across
      major apps.
Change-Id: Ie275f5c37998a9d88e5ccde7af043443cbc4d94c