Add RemoteLockscreenValidationFragment to help retain remote lockscreen am: 2eb8ed24

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/22390454



Change-Id: I58487aef2bc252448119e48c7a2f2bedc3a710b9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>