Add 2 functions for Telit and Quectel modems:
  - disableVoiceSupport: disable voice support (IMS and CSFB) and enable SMS only registration flag.
  - getVoiceSupport: get voice support configuration for the current radio.

Switched to the separate fields for SIM MCC and SIM MNC
after a code review.

Extended the implementation of "getSimCarrierCode" to detect the carrier
(home network) based on the MCC/MNC combination.

Historically mPower used ICCIDs to detect the carrier and apply the
carrier-specific settings. ICCIDs are known for Verizon and AT&T, but
the list of known ICCIDs is not exhaustive.

This change allows the firmware to detect more AT&T SIM cards by using
the MCC/MNC combinations (PLMN IDs) when ICCID is not recognized.

Limitation: The SIM shall be relatively new and report its MNC length,
otherwise MCC/MNC can't be determined and so the carrier code.

Added an ability to read the PLMN ID (MCC/MNC combination) of the home
carrier from the SIM.

SIM PLMN ID is a part of the IMSI that contains identifier of the home
network. PLMN ID in turn consists of 3-digit MCC (country code) and
2-or-3-digit MNC (network code). The length of the MNC is stored in the
SIM Elementary File called "Administrative Data" (EFad for short).

The purpose of the new functions is to extract PLMN ID from the SIM
if this information is available.

Refactoring after review

Refactoring common functions, telit and quectel functions related to CEMODE switching

Added CEMODE switching support for Quectel radios

Changes after a code review.

Changes after a code review