Add support for CO2 emissions compsets with CAM7

[klindsay28]

Description of changes

Use prognostic CO2 in CO2 emissions compsets with CAM7.

Specific notes

Contributors other than yourself, if any:

• none

CTSM issues resolved or otherwise addressed, if any:

• There is not a corresponding CTSM issue for this.

If answers are expected to change, describe (delete this line otherwise):
Answers change in CO2 emissions compsets with CAM7, which are
under development and not in use yet.

Any user interface changes (namelist or namelist defaults changes)?
Changes co2_type to 'prognostic' in CO2 emissions compsets with CAM7.

Testing planned or performed, if any:
ERS_Ld5 and SMS_D_Ld2 tests in an 1850 CO2 emissions compsets with CAM7 pass.

Requirements before merge:

• I have followed the CTSM contribution guidelines.

• The code in this PR branch builds with no errors.
• The code in this PR branch runs with no errors. Briefly describe tested configuration(s):
• This either (a) does not change answers, (b) it only changes answers at roundoff level, or (c) I have performed a scientific evaluation of the answer changes. Which?:
  This only changes answers in CO2 emissions compsets with CAM7,
  which have not been vetted yet. This PR is a step towards enabling them.

• I have reviewed relevant parts of the CLM documentation Tech Note or User's Guide to determine if anything needs to be changed or added. If it does, describe:
• This PR either (a) does not create a need to update the documentation or (b) includes required documentation updates (see guidelines for contributing documentation). Which?:

[wwieder]

Thanks @klindsay28 , will there be additional changes to CMEPS or other submodules that we need to bring in?

@ekluzek this one-liner seems simple enough, but there may be additional infrastructure / testing we need to support?

[klindsay28]

I submitted a 1-line PR to CMEPS today, ESCOMP/CMEPS#658.
That one, like this one, is only relevant for fully coupled CO2 emissions compsets with CAM7.
So I imagine that you'll ultimately pull in an updated CMEPS that has this,
but I don't think it will matter to non-CESM clones of CTSM.
(This statement is based on my understanding that non-CESM clones of CTSM are for
running CTSM only composts, i.e. not fully coupled compsets.)

There are also changes to CAM and MOM_interface, but it doesn't look like these are submodules of CTSM.