Merge "Fullscreen image preview (Part 1)" into ub-launcher3-master am: 3ba70d18f2 am: 853e2b5357

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/WallpaperPicker2/+/11261779

Change-Id: I855e55e22b6091ccde627a0b5d15d61821109fcf