Merge "Add ENABLE_SCRIM_FOR_APP_LAUNCH feature flag." into sc-dev am: 28e39335bc am: d2e9de7fa8 am: a1c8952dea

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

Change-Id: Ic553f6cd137a128fef36438639db255d1f98b736