Implement Harrington & Garaud option for Thermohaline

[evbauer]

Add in modifications due to magnetic fields as calculated in https://ui.adsabs.harvard.edu/abs/2019ApJ...870L...5H/abstract

Adrian Fraser has a python implementation for this that we should be able to port into fortran for MESA. This will then lay the groundwork for starting to work on implementing https://ui.adsabs.harvard.edu/abs/2023arXiv230211610F/abstract

See https://github.com/afraser3/problems-with-parasites and specifically
https://github.com/afraser3/problems-with-parasites/blob/3be4d76163afaf087de7e252b527f3bb198acb00/python/parasite_model.py#L193

[evbauer]

This is mostly done on the thermohaline hackathon branch. We just need to promote the hard-coded magnetic field value to an optional input parameter for the thermohaline calls, and implement some inlist options associated with setting the field.

[afraser3]

Do we want to promote the model parameters (like K_B = 1.24) to inlist options in case users want to fiddle with that? I think the original Brown et al implementation similarly had their model parameter as an inlist option.

(Edit: Matteo pointed out that these are the values that agree with simulations, and thus it is reasonable to leave them hard-coded in.)