[Status bar refactor] Implement the lookup from network type to RAT icon

This CL adds the ability to map from network type to icon used to
display the RAT indicator (LTE, 3G, etc.). This process starts by
consuming TelephonyDisplayInfo and using the SettingsLib
MobileMappings.java utilities to map all of the telephony Network Types
to TelephonyIcons.java.

1. Add an injectable MobileMappings proxy
2. Add support for generating the MobileMappings.Config class under the
   same conditions that NetworkController does.
3. Thread all of the mobile mappings to the MobileIconGroup in
   MobileIconViewModel
4. A bunch of tests

Test: atest MobileIconInteractorTest
Bug: 240492102
Change-Id: I38e917cfa1c98bd86258061defa89cc8705816e0