Scrolling recents to next/prev page focuses next/prev node

Recents did not report that it finished scrolling to Talkback so it did
not focus the next item. Now sending the accessibility event when
scrolling will focus the next node.

Test: talkback on, open recents with tons of apps, scroll to bottom app,
keep swiping left until multiple tasks move down
Bug: 37005488
Change-Id: I07e8d686e7cc0f1a43f13769181d4c7cb87853e8