♻️ Refactor tf averaged turn geometry

[chris-ashe]

This pull request refactors the naming conventions for several variables related to toroidal field (TF) coil turn and cable dimensions throughout the codebase and documentation. The main goal is to improve clarity and consistency by replacing older variable names (t_turn_tf, t_cable_tf, etc.) with new, more descriptive ones (dx_tf_turn_general, dx_tf_turn_cable_space_general, etc.). The changes affect documentation, code, input handling, and output files.

🔄 Renames

t_turn_tf_is_input -> i_dx_tf_turn_general_input
t_turn_tf -> dx_tf_turn_general
t_cable_tf_is_input -> i_dx_tf_turn_cable_space_general
t_cable_tf -> dx_tf_turn_cable_space_general

There is still some underlying functionality used for CORC cables that I will refactor in another PR

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 78.94737% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 46.10%. Comparing base (ef0bd6e) to head (f9647e2).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
process/superconducting_tf_coil.py	80.00%	5 Missing ⚠️
process/stellarator.py	0.00%	2 Missing ⚠️
process/io/plot_proc.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3885      +/-   ##
==========================================
- Coverage   46.39%   46.10%   -0.29%     
==========================================
  Files         123      123              
  Lines       28167    28671     +504     
==========================================
+ Hits        13067    13220     +153     
- Misses      15100    15451     +351     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.