Merge "Enable vendors to add preference controllers in mobile network...

Merge "Enable vendors to add preference controllers in mobile network settings" into udc-dev am: 89e829e3

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/23324419



Change-Id: I17069f20447108b5346fc7246288e8ba93b35f60
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>