Seperate cesm preview namelists out

[ekluzek]

Description of changes:

• Please add an explanation of what your changes do and why you'd like us to include them.

This is preliminary work on moving the cesm postprocessing script into a preview_namelists section and a runtime section.

This is work on #371
Also add #399 here as well

All PRs Checklist:

• Have you followed the guidelines in our Contributor's Guide?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you made sure that the pre-commit checks passed (#8 in Adding Notebooks Guide)?
• Have you successfully tested your changes locally when running standalone CUPiD?
• Have you tested your changes as part of the CESM workflow? Tested, but currently fails
• Once you are ready to have your PR reviewed, have you changed it from a Draft PR to an Open PR?

[ekluzek]

@mnlevy1981 points out that we should have a shared script used by both, that does these initial steps here, something about cesm_import_xml_vars.sh.

With it being executed something like...

. ./cesm_import_xml_vars.sh

It could also be made into a subroutine and exercised that way.

[ekluzek]

It looks like this section doesn't need to be here.

[ekluzek]

In talking with @mnlevy1981 we thought the name should be something like:

cesm_generate_cupid_config_files.sh

[ekluzek]

The problem I was seeing with this for the conda environment, might be explained by adding a

. ./env_mach_specific.sh

call here to make sure the environment is setup as it's needed to be for the CESM case. This is something that's done in the case.cupid script in the CASEROOT.