[Sb refactor] Support NetworkName in new mobile pipeline

The network name can come from one of 3 places:
1. TelephonyManager.ACTION_SERVICE_PROVIDERS_UPDATED, which passes an
   intent containing a network name which we can derive
2. ServiceState.getOperatorAlphaShort(), from the service state changed
   telephony callback
3. A default value, set in the framework config
   `lockscreen_carrier_default`

Based on the implementation that currently lives in
`MobileSignalController`, we were only using `NetworkName` a.k.a.
`EXTRA_SPN`, and not `NetworkNameData` a.k.a. `EXTRA_DATA_SPN`.
Therefore this CL only adds support for the former.

The front end does not consume this piece of data yet, since it is only
needed for QuickSettings. Future CLs will add support for a
LocationBasedMobileViewModel (similar to Wi-Fi), which can then start
consuming the values.

Test: MobileConnectionRepositoryTest
Test: DemoMobileConnectionsRepositoryTest
Test: MobileIconInteractorTest
Bug: 238425913
Change-Id: I04fa90bf7b52aa992f9721c7301f541f6085cf68