Merge "Camera: Improve documentation for 3A regions" into tm-dev am: 3a7a59da am: 669d7764

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



Change-Id: I795d8371c76f72f25a88835e23d7f1a80ab982f4
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>