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

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

Change-Id: Iecfbdc781852e24aafb92744f9a3de4ff5cbbd00