[SuwLib] Tap on list items must always register

When talkback is enabled, sometimes tap on list items does not result in
the whole item being selected by talkback. (No green border around the
item)

- This was caused because focus was enabled on richtextviews by
  ExploreByTouchHelper.
- Fix is to avoid creating LinkAccessibilityHelper when focus is
  disabled and text has no links

bug:29538956
Change-Id: I795a1f621635e8e8e5ee2fa60d2eafc02144b84a