Fix the a11y focus problem in a long list page

While a page is scrolling to the target position, the target can't
request a11y focus, and the highlight blink animation at the moment is
also invisible.

The patch is to skip the unseen highlight animation and focus operation
when onBindViewHolder() is called before scrolling. Therefore, when the
scrolling stops, the scroll listener will notify the item changed and
onBindViewHolder() will be called again to do the operations.

Also decrease the delay time of the scrolling start to make the a11y
smoother.

Bug: 318459003
Test: manual, robotest
Change-Id: Ie55b2edeb7e1feaaadb5e670f39f07f6f17b92b9