Expose Carrier Name Override CarrierConfig Values

These CarrierConfig values are needed for a
CC app to override the SPN dynamically. Since
Carrier names are very complicated, it's extra
important that these values be exposed so that we
can properly enforce correct behavior through CTS.

Bug: 73734601
Test: compilation (no functional change)
Change-Id: I26dab1bd32d1d5273f707a37026cffca7fd639a3