docs and formatting for fake_image.py, girsmconf.py, jwst_utils.py

[KostasValeckas]

Updated docs and formatting for fake_image.py, girsmconf.py, jwst_utils.py .

This is a continuation from PR's #229 and #240 as agreed with @gbrammer .

Specifically:

• added missing / completed incomplete docstrings using AI tools.

• went through formatting using black.

• removed or edited some unused parameters

Very little done to fake_image.py .

For girsmconf.py, in the CRDSGrismConf class, I had issues with determining the interplay between the many DISP methods (DISPX, INVDISPX) and all alike, and the model evaluation methods that are being employed within (specially the inverse). I had made a best-attempt, and left some TODO comments on where I got stuck. Many of these methods are repetitive, so please feel free to let me know if/where the docs are incorrect (and if possible what corrections should be done) - I would happily to do another iteration and apply any feedback myself.

In jwst_utils.py, some parameters were never used. These were mostly keyword args to other methods. I have exchanged hardcoded keyword args with the unused parameters where the intention for this was clear. All relevant parts are marked with TODO comments for review.

[gbrammer]

Thanks @KostasValeckas ! Yes, the logic of the grismconf polynomials is very hard to follow. I've updated the docstrings accordingly. Not necessarily such that you can understand exactly what they do but at least the basic description of the inputs and outputs.