Update CMIP7 unit tests

[mauzey1]

Resolves #879

CMIP7 unit tests will now use tables from cmip7-cmor-tables, which is now a submodule in this repo.

This will also allow the adding of mip_era and data_specs_version as global variables if they are defined in the CV even if they are not listed in required_global_attributes.

@matthew-mizielinski Would you mind reviewing this PR?

[YanchunHe]

Thanks for the great effort. This is very useful!

As we are using the library's Fortran API, could you also provide a Fortran version of the test file?

I had some earlier test, and it seems some source code is still hard-coded with CMIP6_CV.json.

[mauzey1]

@durack1 I've migrated some changes to the CMIP7 CV in TestTables from #851 to here. Any other CV changes that I should move?

[mauzey1]

@matthew-mizielinski Are you okay with these changes? If so, we can have these changes merged.

@durack1 Are these change sufficient enough that we can close issue #843 and PR #851?

@YanchunHe We'll create another issue for creating a Fortran CMIP7 unit test and have it handled in a separate PR.

[durack1]

@mauzey1 as many of the parts (CVs, tables, etc) are still moving, it might be best to merge these changes, have a nightly created and for testing to continue before a release is minted. @matthew-mizielinski and @JamesAnstey are you ok with this approach?

[matthew-mizielinski]

Hi @mauzey1, I think this looks ok to me. I will note that on second review that you've turned some CMIP6 style tests into CMIP7 style tests rather than adding tests -- this could allow issues with the CMIP6 style functionality to creep in, but the risk of this will be low.

@mauzey1 as many of the parts (CVs, tables, etc) are still moving, it might be best to merge these changes, have a nightly created an for testing to continue before a release is minted. @matthew-mizielinski and @JamesAnstey are you ok with this approach?

Yes, I don't think we need a release until some of the issues related to repacking have been looked at.

[durack1]

@mauzey1 apologies for the delay, let's get this merged and into nightly