Add full land variable set for model vs model comparison

[chengzhuzhang]

Description

Close #999
This PR fully support native ELM output for model vs model comparison by expanding from ~94 variables to all 353
variables from the land group's CSV file.

Key Changes

1. Variable Expansion

• Before: 94 ELM variables in lat_lon_land_model_vs_model.cfg
• After: 422 total variables (94 original + 283 new and additional )
• New Variables Added: 283 ELM variables from zppy_land_fields.csv

2. Unit Conversion System

Proper Conversions for Spatial Maps:

• Carbon Flux Variables: gC/m²/s * 86400 → gC/m²/day
• Carbon State Variables: gC/m² / 1000 → kgC/m²
• Nitrogen/Phosphorus Flux: gN/m²/s * 86400 → mgN/m²/day
• No Conversion Variables: Direct rename for energy fluxes, physical states, etc.

3. Data-Driven Contour Levels

• Used actual PI control data:
  /lcrc/group/e3sm2/ac.zhang40/E3SMv3/v3.LR.piControl_land_ilamb/post/lnd/native/clim/50yr/
• Calculated 5th/95th percentile-based contour levels from real data
• Generated 16 realistic contour levels per variable

4. Variable Organization

By Functional Groups (from CSV):

• Aerosol Flux/State: BCDEP, DSTDEP, SNOBCMCL, etc.
• C Flux: AGNPP, AR, BGNPP, CH4PROD, ER, GPP, HR, NBP, NPP, etc.
• C State: CWDC, FROOTC, LEAFC, SOIL1C, WOODC, etc.
• Energy Flux/State: EFLX_LH_TOT, FSA, FSH, TSA, etc.
• Fire: FAREA_BURNED, PFT_FIRE_CLOSS, etc.
• H2O Flux/State: QRUNOFF, RAIN, SNOW, TWS, etc.
• N Flux/State: ACTUAL_IMMOB, F_DENIT, GROSS_NMIN, SMINN, etc.
• P Flux/State: ACTUAL_IMMOB_P, GROSS_PMIN, SMINP, etc.
• Physical State: ALT, FSNO, ZWT, etc.
• Veg State: BTRAN, ELAI, TLAI, etc.
• Urban, Winds, Pressure: Various specialized variables

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

If applicable:

• New and existing unit tests pass with my changes (locally and CI/CD build)
• I have added tests that prove my fix is effective or that my feature works
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected)

[chengzhuzhang]

@thorntonpe Hi, Peter, I have this PR for e3sm_diags to generate many more variables to match those requested for zppy's global time-series plots. Could you view the results to see if there are obvious problems that I should fix? Thank you!

[chengzhuzhang]

I need to merge this for the zppy weekly test to get prepared for e3sm-unified, we can fine tuning this feature before the final e3sm diags v3.1 release.