Configuration: No validation

Most of the AMF configuration values are not validated, i.e. the validate value is not overriden and also the regex validators of string values and the intervals of int values are not set accordingly.

We should implement this similar to SMF, so that the user is not confused when there are mistakes during PDU session establishment because of an illegal configuration. These kind of scenarios are really hard to debug, which is why the validation is so useful. Also, it may prevent security issues.