Merge "Let Talkback announce to the user when changing dark/light theme" into sc-v2-dev am: 13673f84a6

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/ThemePicker/+/16373914

Change-Id: I724156bdce90065be24e9194ade95c5610aee6a4