rename and improve description of weathering rates

[tabeado]

Purpose of this PR

p33_co2_rem_rate and s33_co2_rem_rate currently have the same description, albeit meaning different things.

To make it more accessible and have different names, I suggest to rename the latter to s33_co2_rem_fraction, as it actually provides the (theoretical) fraction weathering each year. Alternatively, we could call it p33_co2_rem_exponent?

The PR also changes the description in the declarations.

Happy to further improve the description or names based on your suggestions.

If you agree to the renaming, I will also need to adjust it in remind2.

Type of change

• Bug fix

Checklist:

• My code follows the coding etiquette
• I performed a self-review of my own code
• I explained my changes within the PR, particularly in hard-to-understand areas
• I checked that the in-code documentation is up-to-date
• I adjusted the reporting in remind2 where it was needed
• I adjusted forbiddenColumnNames in readCheckScenarioConfig.R in case the PR leads to deprecated switches
• All automated model tests pass (FAIL 0 in the output of make test)
• The changelog CHANGELOG.md has been updated correctly

@strefler @amerfort

for reference @VerenaHof @robertsalzwedel

[tabeado]

Updated suggestion to be approved by @strefler:

• We renamed s33_co2_rem_rate and p33_co2_rem_rate to s33_rock_weath_rate_ambientT and p33_rock_weath_rate:
  - The scalar provides the fraction of stone weathering each year at ambient temperature. This is now reflected in the name.
  - The parameter provides the fraction of stone weathering each year for the two climate grades.
• We simplify the equations q33_EW_onfield_tot and q33_EW_emi:
  - The logarithmus in the old p33_co2_rem_rate and the exponential functions in these equations cancel out. We suggest to avoid the exponential formulation. Or was there a computational GAMS reason to write it this way?
  - The change means that the content of p33_rock_weath_rate has a direct simple interpretation (changed from the exponent of the exponential function to simply the rock fraction weathering per year)

[tabeado]

Test run with the new formulation: /p/tmp/tabeado/remind_clean_new/remind/output/SSP2-PkBudg650-EW_2024-12-18_19.04.40