Write current scan point to MFILE

[timothy-nunn]

Description

Adds a new MFILE variable that contains the current scan variable.

TODO: utilise scan variable for plotting, remove out_name

Bugfixes

• nsweep_2 was being written out 3 times for some reason
• 2D scans would not run because sv.data.description was being used instead of sv.description

Changes
There is no concept of out_name anymore: you plot the variable you scan exactly.

This changes scan variable 17

b_tf_inboard_max = (17, Area.C, "b_tf_inboard_peak_symmetric")

which was plotting b_tf_inboard_peak_symmetric, but this makes no sense because it was not the scanned variable. I think this change is ok because we should not be scanning one variable and then plotting another. If that functionality is desired, people can write their own small plotting script.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 4.16667% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.97%. Comparing base (9592524) to head (c1dad7e).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
process/core/io/plot/scans.py	0.00%	12 Missing ⚠️
process/core/scan.py	8.33%	11 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4611   +/-   ##
=======================================
  Coverage   49.97%   49.97%           
=======================================
  Files         151      151           
  Lines       29929    29917   -12     
=======================================
- Hits        14956    14951    -5     
+ Misses      14973    14966    -7     

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[je-cook]

I'm happy but @chris-ashe might have a comment about scan no 17 change