Encode oper/fc as control forecast

[tweska]

📋 Metkit Documentation 📋
https://sites.ecmwf.int/docs/metkit/pull-requests/PR-262

[codecov-commenter]

Codecov Report

❌ Patch coverage is 67.64706% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.53%. Comparing base (484e1a5) to head (705badb).

Files with missing lines	Patch %	Lines
...b/backend/deductions/numberOfForecastsInEnsemble.h	29.41%	12 Missing ⚠️
tests/mars2grib/encoding/001_oper_fc_as_control.cc	85.71%	5 Missing ⚠️
src/metkit/grib2mars/mappings/rules/misc.h	0.00%	2 Missing ⚠️
...s2grib/backend/concepts/ensemble/ensembleMatcher.h	60.00%	2 Missing ⚠️
.../mars2grib/backend/deductions/perturbationNumber.h	80.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #262      +/-   ##
===========================================
+ Coverage    42.30%   42.53%   +0.23%     
===========================================
  Files          462      463       +1     
  Lines        20845    20875      +30     
  Branches      1509     1509              
===========================================
+ Hits          8819     8880      +61     
+ Misses       12026    11995      -31     

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