Cleanup Diffusion config

[havogt]

• Remove thslp_zdiffu and thhgtd_zdiffu from the Fortran bindings as they are not used
• Raise an error if compute_3d_smag_coeff as we don't support this mode
• Add hdiff_w_efdt_ratio to the Fortran bindings (though for now we don't have any experiment that deviates from the default value)

[havogt]

wondering if we should cherry-pick the changes in config from the configuration PR #936

[havogt]

cscs-ci run default

[havogt]

cscs-ci run distributed

[jcanton]

for a moment I thought you had removed thhgtd_zdiffu and thslp_zdiffu from the entire codebase :-)
LGTM

[havogt]

cscs-ci run default

[havogt]

cscs-ci run distributed

[github-actions]

Mandatory Tests

Please make sure you run these tests via comment before you merge!

• cscs-ci run default
• cscs-ci run distributed

Optional Tests

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• cscs-ci run benchmark-bencher

To run tests and benchmarks with the DaCe backend you can use:

• cscs-ci run dace

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• cscs-ci run extra

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