Include AOSP telephony apps in mainline_system.

These apps are included on all mainline devices. Including them
necessitates splitting telephony.mk into two pieces, as "rild"
installs on /vendor.

Bug: 80410283
Test: lunch mainline_arm64; m nothing
Change-Id: Id4f1684604c71e853c8096e9a6992e65b6dfefed