feat: add conf2uedata tool for generating .*.nvram

This patch adds the conf2uedata tool for generating .ue.nvram* .ue.emm.nvram*
and .usim.nvram* files from a textual configuration file.

The configuration file define most usefull values like plmns, mnc, mcc, msin, K,
OPc for several users.
The files generated will always ends with a number corresponding to the user
entry in the configuration file.

This breaks oai5g because other script have not be updated for using
conf2uedata.
This breaks also the at_nas_ue command.

Examples of configuration files are in openair3/NAS/TOOLS/