Fall back to reading config_satellite_sim_identifier from device config

Can't override resource overlay config from adb. Thus, add a code to
fall back to read this config from device config when the overlay config
is empty && mock modem is enabled on the device.

Bug: 307905732
Test: manually test and verify the log as exptecd. SMS, MMS, call with
live network.

Change-Id: I807b93bb270e4390f4b616bb93bfa313dfe52f68