Move guts of buildlib/buildnml to own python/ctsm module

This also should be coordinated with some work that Mike Levy is doing in CESM to have automatic checking of python modules with pylint. So some of this should happen after that work is done so that it's done the same way.

But, we should move the guts of buildlib and buildnml to their own python modules under python/ctsm that will then have automatic checking by pylint (and eventually black). As part of this we should also run them through pylint and clean up the current issues.

So the steps to this are:
- Run buildnml and buiildlib through pylint and fix the errors
- Run them through black
- Move the guts to python/ctsm modules called with a wrapper for buildnml/buildlib
- Take in the changes that Mike Levy works on for how buildnml/buildlib should look for all CESM components

I'm not sure which of the last two should happen first. We should update this issue when we hear more from CSEG and Mike Levy on how components should make their buildlib and buildnml scripts to look like.