Complete the FATES-CLM nitrogen coupling

[slevis-lmwg]

Description:

I started this PR with changes needed in ESCOMP/CTSM#3409.
So far that's just the renaming of
prt_carbon_allom_hyp to fates_c_only
prt_cnp_flex_allom_hyp to fates_cn

The corresponding ESCOMP issue:
ESCOMP/CTSM#3378

Resolves #1454

Collaborators:

@rgknox
@adrifoster

Expectation of Answer Changes:

I do not expect answers to change as a result of this PR alone; however, I expect answers to change for fates_parteh_mode = 2 as a result of the corresponding ESCOMP PR. So far I have not seen such diffs, while I have seen diffs for fates_parteh_mode = 1.

Checklist

All checklist items must be checked to enable merging this pull request:

Contributor

• The in-code documentation has been updated with descriptive comments
• The documentation has been assessed to determine if updates are necessary

Integrator

• FATES PASS/FAIL regression tests were run
• Evaluation of test results for answer changes was performed and results provided
• FATES-CLM6 Code Freeze: satellite phenology regression tests are b4b

If satellite phenology regressions are not b4b, please hold merge and notify the FATES development team.

Documentation

• Technical Note update:
• User's Guide update:

Test Results:

CTSM (or) E3SM (specify which) test hash-tag:

CTSM (or) E3SM (specify which) baseline hash-tag:

FATES baseline hash-tag:

Test Output:

[slevis-lmwg]

@rgknox I found a moment to come back and look at my progress in these PRs:

• You recently brought up the naming choice of the two indices in lines 71-72. I see that I likely should have named the second one fates_cnp, but I will refrain from making changes until we follow up and agree on something.
• Before we meet, I still have two unchecked boxes in Completing the FATES-CLM nitrogen coupling ESCOMP/CTSM#3378 (comment), though we could also potentially touch base before I resolve them. Currently I have Friday afternoon Pacific Time (and most afternoons next week) available.
• Regardless, I continue to make slow progress due to the ctsm5.4 preparations.