The numeric fields in the +COPS=? response were relying on a very weak
parsing logic, assuming that they were single-digit numeric values and
not using the common string to integer conversion utilities.
This commit improves the conversion from the 3GPP/ETSI defined network
availability and access technology values to the MM defined ones,
providing enum-based matches even if the numeric values are the same.
The commit also fixes the parsing of access technology values > 10,
required to report 5G related values.
2c8cfb4768