Export CO2 value to the land model via coupler

[jimmielin]

Tag name (The PR title should also include the tag name):
Originator(s): @jimmielin assisted-by claude-fable:5

Description (include issue title and the keyword ['closes', 'fixes', 'resolves'] and issue number):

• Add co2_diagnostic_export utility scheme to pass the prescribed_volume_mixing_ratio_of_co2 prescribed via prescribe_radiative_gas_concentrations to the coupler (this is a scalar value)

CAM just does this in camsrfexch.F90

cam_out%co2diag(:ncol) = chem_surfvals_get('CO2VMR') * 1.0e+6_r8

List all namelist files that were added or changed:

List all files eliminated and why:

List all files added and what they do:

A       schemes/utilities/co2_diagnostic_export.F90
A       schemes/utilities/co2_diagnostic_export.meta
  - new scheme

List all existing files that have been modified, and describe the changes:
(Helpful git command: git diff --name-status main...<your_branch_name>)

M       suites/suite_cam4.xml
M       suites/suite_cam5.xml
  - wire scheme up to CAM4/5 suite

M       suites/suite_cam7.xml
  - add scheme up to CAM7 suite along with the rest of the commented out ones

List all automated tests that failed, as well as an explanation for why they weren't fixed:

Is this an answer-changing PR? If so, is it a new physics package, algorithm change, tuning change, etc?

If yes to the above question, describe how this code was validated with the new/modified features: