DM-22114: Remove deprecated makeDistortedTanWcs

[arunkannawadi]

This PR removes the function makeDistortedTanWcs and merges its unit tests with those of computePixelToDistortedPixel.

[parejkoj]

I'm confused: why didn't you keep the existing ComputePixelToDistortedPixelTestCase and remove the MakeDistortedTanWcsTestCase class instead? It's hard to tell with this diff whether the new class is exactly the same as the deleted one or not.

[arunkannawadi]

The messy diff happens to be due to git trying to behave too smart, it looks like. I unstaged the previous changes and removed the MakeDistortedTanWcsTestCase completely and edited the ComputePixelToDistortedPixelTestCase, but because the line numbers coincide, git really thinks I edited former one and deleted the latter one. In any case, the git diffs are messy either ways the two test cases are merged.

[arunkannawadi]

Okay, I've split the changes into two commits that make more sense logically. The PR diff is still messy as before, but the commit diffs might be helpful to see the differences.

[parejkoj]

One minor comment about a docstring, but otherwise this looks good. Thank you for the detailed comments in the new tests regarding how you generate and apply the transforms, they are very helpful.