c_tf_turn error catching

[clmould]

Description

Check that ixc = 60 (c_tf_turn) is not used when i_tf_turns_integer is 1
Check that ixc = 60 is not used with icc = 77

Updated version of #3114 - this PR was very outdated. Will close #724

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 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.83%. Comparing base (2f754a2) to head (3f9d78b).
⚠️ Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
process/init.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4034      +/-   ##
==========================================
- Coverage   45.88%   41.83%   -4.05%     
==========================================
  Files         123      123              
  Lines       29087    40980   +11893     
==========================================
+ Hits        13346    17144    +3798     
- Misses      15741    23836    +8095     

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[jmorris-uk]

I would suggest this has more information e.g.

Cannot use iteration variable 60 (TF coil current per turn, c_tf_turn) and constraint 77 (maximum TF current per turn) simultaneously.

[jmorris-uk]

Maybe something like this for more useful information.

Iteration variable 60 (TF current per turn, c_tf_turn) cannot be used with the TF coil integer turn model (i_tf_turns_integer == 1) as it is a calculated output instead for this model. However, the maximum current per turn can be constrained with constraint 77.