Add ability to select solvent model to C api

[TyBalduf]

Is your feature request related to a problem? Please describe.
Currently, the C-api has a setSolvent functions, which allows setting GBSA implicit solvation. It would be useful to be able to select the solvent model among GBSA, ALPB, COSMO, and CPCM-X (might be a little more involved, since it requires a 2nd SCF loop).

Describe the solution you'd like
Add a parameter to setSolvent allowing the solvation model to be specified.

Describe alternatives you've considered
Could work around by launching the xTB executable and just parsing the output for the portions I need, but the API is definitely more convenient when working in C/C++

If possible state how you can assist in providing data or code to to implement the feature
Plan to put together a code review for this. Might need some pointers on how to handle updating the API version or whether this should just be added as a new setSolventWithModel.

Could also use some input on how to best handle CPCM-X. Current plan is to just leave it to the user to handle running the initial COSMO solvent=infinity SCF loop and then a second SCF loop with CPCM-X and their desired solvent.