[LivePicker 2/n] Add LiveWallpaper preview support

Create a new LivePreviewFragment with the same UI and
functionality of Android's LivePicker.

Note that there's still redundancy between
ImagePreviewFragment and LivePreviewFragment, follow up
CLs will clean this up and share as much as possible.

Still missing is support for delete and settings action
buttons. The new LivePreviewFragment won't be hooked up
until all the functionality is implemented.

Bug: 141391722
Change-Id: I859f9122c368c01575c23f73a80ffdb519ef0e71
15 files changed