Merge "Camera: Improve documentation for 3A regions" into tm-dev am: 3a7a59da

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/17450690



Change-Id: I7293ecd43a0060aa5409b172a613178330f47868
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>