feat(amf): logging level can be setup at run-time and not build-time

For the moment, I don't want to merge it like this.

I want to use the oai-cn5g-common-src that Romain started and build on this. But I want to start the discussion.

Here I have only one log level for the whole NF.

Linked to MR on the common-src repo --> oai-cn5g-common-src!3 (merged)