More generic x-point check

[geograham]

Linked Issues

Closes #4161

Note for reviewer: I had thought this might be used in which_legs of Legflux but I am not sure.

Image below, to show rough use - checking for intersections between the closed flux surface and a tangent line at the x-point.

Checklist

I confirm that I have completed the following checks:

• Tests run locally and pass pytest tests --reactor
• Code quality checks run locally and pass pre-commit run --from-ref develop --to-ref HEAD
• Documentation built locally and checked sphinx-build -W documentation/source documentation/build

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.69%. Comparing base (447515f) to head (fb794f3).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4172      +/-   ##
===========================================
- Coverage    78.95%   78.69%   -0.26%     
===========================================
  Files          244      244              
  Lines        29322    29352      +30     
===========================================
- Hits         23150    23099      -51     
- Misses        6172     6253      +81     

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[github-actions]

⚠️ Warning Report

Found 0 new warnings, 0 fixed warnings. 🎉

All warnings (1)

On collect

• /home/runner/work/bluemira/bluemira/bluemira/codes/openmc/solver.py:60: DeprecationWarning: In 3.13 the default auto()/generate_next_value will require all values to be sortable and support adding +1 and the value returned will be the largest value in the enum incremented by 1

[je-cook]

Thanks!