[Mobile] Add SPN to network name calculation

An oversight from the initial migration away from
MobileSignalController; NetworkNameModel was only considering the
DATA_SPN when calculating the network name, but it needed to consider
_both_ the SPN and the DATA_SPN.

Also addressed the fact that the tests were calling the same function
and wouldn't catch this issue.

Test: MobileConnectionRepositoryTest
Bug: 350812372
Flag: NONE bugfix
Change-Id: I492ab0d77c93f371589abc56a3faca9bc516a407