cs fatigue data class and setting up use of datastructure elsewhere t…

[clmould]

…o allow DataStructure use

Description

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 89.02439% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.55%. Comparing base (2899a60) to head (424653a).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
process/core/caller.py	28.57%	5 Missing ⚠️
process/core/scan.py	20.00%	4 Missing ⚠️
process/core/solver/constraints.py	96.59%	3 Missing ⚠️
process/core/solver/solver_handler.py	33.33%	2 Missing ⚠️
process/core/final.py	66.66%	1 Missing ⚠️
process/core/solver/evaluators.py	50.00%	1 Missing ⚠️
process/main.py	80.00%	1 Missing ⚠️
process/models/pfcoil.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4173      +/-   ##
==========================================
- Coverage   49.56%   49.55%   -0.02%     
==========================================
  Files         148      148              
  Lines       29719    29715       -4     
==========================================
- Hits        14731    14724       -7     
- Misses      14988    14991       +3     

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