JP-4372: Fix edge cases in bounding box computations

[mcara]

Fixes a crash in the JWST pipeline which happens when one of the images has three sources detected and they lie on almost a straight line. The convex hull of these points is a triangle with minimal height resulting in the spherical polygon being considered degenerate since all vertices lie on a great circle.

This PR replaces convex hull with a bounding rectangle of height or with of no less than 1 pixel only when the spherical polygon created with the convex hull is degenerate.

Closes JP-4372

Regression tests:

• JWST: https://github.com/spacetelescope/RegressionTests/actions/runs/27257813514
• JWST (CRDS_CONTEXT=jwst_1555.pmap): https://github.com/spacetelescope/RegressionTests/actions/runs/27310278928
• Roman: https://github.com/spacetelescope/RegressionTests/actions/runs/27257905170

[codecov]

Codecov Report

❌ Patch coverage is 46.66667% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.97%. Comparing base (e6728a1) to head (b3e497d).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
tweakwcs/wcsimage.py	46.66%	32 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #254      +/-   ##
==========================================
- Coverage   92.35%   90.97%   -1.39%     
==========================================
  Files          11       11              
  Lines        2015     2072      +57     
==========================================
+ Hits         1861     1885      +24     
- Misses        154      187      +33     

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[tapastro]

I can't say that I fully follow the new code - it seems like there are instances were 0.5 is added or removed from array values to generate some non-zero areas, but I don't understand what units x and y typically have here - pixel coordinates, or something else? It's not immediately clear to me that 0.5 is a small value. But I think the concept appears sound.