Merge "Add ENABLE_SCRIM_FOR_APP_LAUNCH feature flag." into sc-dev am: 28e39335bc am: c01e87daf0 am: 23551fbf29

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14987185

Change-Id: Id39a7a6c2d668911d918b50d268a56fcb410306c