iface-modem: new carrier config support

During initialization phase we will allow querying the modem for the
details of which carrier-specific configuration is being used, and
will expose a description string in the API.

In addition to showing the current configuration, we will also allow
automatically switching the configuration based on the SIM card
detected in the device. In order to allow this, plugins/modems will
need to provide the expected mapping between carrier config
description and MCCMNC. This mapping cannot be generic, because
different manufacturers may use different description strings.
9 files changed