Add helper method in phone to get new carrier config key.

Also, add method to return all emergency numbers that have the specified
number.
Flag: This is a cherry-pick from udc-qpr-dev, so no flag is needed.
Test: See other cls for actual tests.
Bug: 281934614
Change-Id: I25f627fdadcbc512e045302a5ba52e3ed8a89cbc