Add configurable values of NR RLC and NR PDCP to the configuration file

This is for the gNB (the UE gets the values from the gNB).

The physical simulators were also adapted (we put the previously hardcoded values that were everywhere in the code into the simulators themselves). I don't think we need to have those values configurable for the simulators, but I can study the possibility to add this if someone tells me it's important (if not important I prefer not to do it, I am not sure if it is trivial to do or not).