Apply top intro preference for face settings page

Do a few things in this cl
- Use correct way to work with controller.
- Refactor xml file.
- Separate content of footer to two parts.
  - First paragraph should become top intro.
  - Rest should keep in footer.

Test: Build apk and see the screen
Bug: 173087905
Change-Id: Icb16dedf6b36542b833527471579aaadb5407d87
Screenshot: https://screenshot.googleplex.com/92Jx6zKyTZU8LJa.png