Enable PLC1901

[je-cook]

Description

enables PLC1901

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 42.85714% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.85%. Comparing base (a3db864) to head (543681e).

Files with missing lines	Patch %	Lines
process/core/io/vary_run/config.py	0.00%	7 Missing ⚠️
process/core/io/in_dat/base.py	0.00%	2 Missing ⚠️
process/core/io/plot/summary.py	0.00%	2 Missing ⚠️
process/core/io/vary_run/tools.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4418      +/-   ##
==========================================
+ Coverage   48.84%   48.85%   +0.01%     
==========================================
  Files         151      151              
  Lines       29406    29390      -16     
==========================================
- Hits        14363    14359       -4     
+ Misses      15043    15031      -12     

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[timothy-nunn]

LGTM

I will just note that I have considered the slight logic change that has been introduced:

• Before: the IN.DAT parameter parsing only discarded the last element if it was empty
• After: the parser discards any element that is empty
  This change should actually make us more robust to IN.DAT's with atypical features.