Add a small FAPI Hex parser utility

Adds a small FAPI hex parser utility nfapi_hex_parser, that takes in a FAPI message hexdump, either from the command line or a file, unpacks it and prints the contents out to the console.

The functions to print the data to the console were added alongside the existing utility functions, for both P5 and P7 messages

This allows the user to quickly check if a message has the valid format to be unpacked in OAI.

The file examples.md contains some examples of execution and output.

This utility is compiled alongside the NFAPI_LIB, as such, it is compiled whenever we compile nr-softmodem, or any other target that uses the NFAPI_LIB