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

Also, add method to return all emergency numbers that have the specified
number.

Test: See other cls for actual tests.
Bug: 281934614
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:e0aee3c0c0957612c7cded4c880c823ef17eb7e3)
Merged-In: I25f627fdadcbc512e045302a5ba52e3ed8a89cbc
Change-Id: I25f627fdadcbc512e045302a5ba52e3ed8a89cbc