Enable Talkback for photo picker

- When pressing a button, Talkback speaks the button text.
- When pressing a photo, Talkback speaks photo's account type,
  user name, and whether the photo is checked or not.
- When double tapping a photo, Talkback speaks the account type,
  user name, and that the photo is checked.

Bug: 25498370
Change-Id: Id43a220a4d5625470ff0ad1ff40a840d9c6bcd84