Varying celestial transforms 3 d

[svensk-pojke]

Adds 3D capability to VaryingCelestialTransform and VaryingCelestialTransformSlit. Submitting PR now to facilitate deployment of Cryonirsp pipeline on DKIST DC stacks. A later upgrade to this code will include additional unit tests for transforms to include round trip pixel-to-world --> world to pixel testing. In addition, I will consolidate the many different VaryingCelestialTransform classes into far fewer, and evaluate the possibility of generic N dimensional VaryingCelestialTransform and VaryingCelestialTransformSlit classes.

[codecov]

Codecov Report

Merging #277 (afc379e) into main (d082995) will decrease coverage by 0.64%.
The diff coverage is 87.14%.

@@            Coverage Diff             @@
##             main     #277      +/-   ##
==========================================
- Coverage   97.09%   96.45%   -0.64%     
==========================================
  Files          37       37              
  Lines        2273     2371      +98     
==========================================
+ Hits         2207     2287      +80     
- Misses         66       84      +18     

Impacted Files	Coverage Δ
dkist/wcs/models.py	96.77% <86.76%> (-3.23%)	⬇️
dkist/io/asdf/converters/models.py	97.95% <100.00%> (ø)

[Cadair]

As long as you pinky promise to come back and write more tests then it's good with me 😉.

Can you add changelog fragment saying that "experimental support" or similar has been added for 3D table models?