❄️ Update cryostat docs

[chris-ashe]

Description

This pull request includes several changes to the naming conventions for cryostat-related variables across multiple files, ensuring consistency and clarity in the codebase. The most important changes involve renaming variables and updating documentation to reflect these changes.

🔄 Namespace changes

Variables

• rdewex -> r_cryostat_inboard
• rpf2dewar -> dr_pf_cryostat
• hcryopf -> dz_pf_cryostat
• zdewex -> z_cryostat_half_inside
• vdewex -> vol_cryostat
• ddwex -> dr_cryostat
• clhsf -> f_z_cryostat
• clh1 -> dz_tf_cryostat

✨ New additions

• vol_cryostat_internal: Represents the internal volume of the cryostat

• cryostat_output(): New function to output the cryostat details in a dedicated function

New output from OUT.dat

🐛 Bugs

• The previous calculation for the volume of the cryostat structure was:

fwbs_variables.vdewex = (
            (2.0 * np.pi * fwbs_variables.rdewex) * 2.0 * fwbs_variables.zdewex
            + (2.0 * np.pi * fwbs_variables.rdewex**2)
        ) * build_variables.ddwex

Which wasnt easy to interpret so a new model for the cryostat structure volume has been introduced which is simply
dividing the cryostat into 2 nested cylinders and taking the internal volume from the bigger one. This caused a 1% change in the calculated volume compared to the tests (810 -> 818 $m^3$)

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.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 38.88889% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 30.84%. Comparing base (c145648) to head (17d23bf).
⚠️ Report is 525 commits behind head on main.

Files with missing lines	Patch %	Lines
process/build.py	8.33%	11 Missing ⚠️
process/io/plot_proc.py	0.00%	5 Missing ⚠️
process/stellarator.py	0.00%	4 Missing ⚠️
process/geometry/cryostat_geometry.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3501      +/-   ##
==========================================
+ Coverage   30.83%   30.84%   +0.01%     
==========================================
  Files          80       80              
  Lines       19322    19325       +3     
==========================================
+ Hits         5958     5961       +3     
  Misses      13364    13364              

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[j-a-foster]

Docs look good.

[j-a-foster]

Regression test failures are acceptable - only constraint variables have changed significantly. Happy for this to be merged.