[DO NOT MERGE] User switcher activity - use immersive mode am: 58c1dab1

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20195509



Change-Id: Ide057461c3834bba86b3dce868014f4070548c5f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>