DO NOT MERGE Add helper method in phone to get new carrier config key. am: e0aee3c0

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/opt/telephony/+/24628058



Change-Id: I9d19d925a80ed7151d02db2f23c333b7acb23e58
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>