Namelist Refactor

[jjuyeonkim]

Description
This is one of multiple PRs to refactor the NDSL's Namelistand NamelistDefaults so that submodules have more ownership over configuration parameters and corresponding default values. NDSL Issue#64

Changes include the following:

• Adds simple dycore tests from yaml and nml files to help test the modified ndsl.Namelist
• A small 'baroclinic_instability' cleanup in tests/main/fv3core/test_init_from_geos.py
• Temporarily points to jjuyeonkim fork to pass CI, to be reverted after resolving NDSL issue #64

Fixes: NOAA-GFDL/NDSL#64 (refactor that affects Pace, NDSL, PyFV3, and PySHiELD).

How Has This Been Tested?
PyFV3 and PySHiELD translate tests run as expected compared to the develop branch. Pace unit tests also pass as expected. Two simple unit tests have been added for checking that the dycore config loads correctly from both input.nml and *.yaml config.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules -- There are changes in Pace, NDSL, PyFV3, and PySHiELD to address this issue. They need to be checked in together.
• New check tests, if applicable, are included
• Targeted model, if this change was triggered by a model need/shortcoming