Add cs alpha beta

[chris-ashe]

Description

Add the CS coil $\alpha$ and $\beta$ dimension variables to calculation and output

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[CoronelBuendia]

It's minor but I think this should read:

z_cs_half / r_cs_coil_inner

Lest z_cs_coil_middle ever be changed from 0.0, this will be one less thing to worry about.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.28%. Comparing base (95c71b6) to head (c998751).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
process/models/pfcoil.py	70.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4670      +/-   ##
==========================================
- Coverage   50.31%   50.28%   -0.04%     
==========================================
  Files         181      181              
  Lines       30458    30525      +67     
==========================================
+ Hits        15326    15348      +22     
- Misses      15132    15177      +45     

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