Add mars2mars mappings for known atmospheric composition params

[tweska]

This PR adds all currently known mapping from the old param to the new param + chem value for atmospheric composition fields. Fields that should map to wavelength are omitted for now, as the value to map to is unknown.

We need more changes in the encoder for this to be useful, this PR will stay as draft until those changes are sorted out.

🌈🌦️📖🚧 Documentation 🚧📖🌦️🌈
https://sites.ecmwf.int/docs/dev-section/multio/pull-requests/PR-245

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 209 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.28%. Comparing base (3016cd7) to head (b714642).

Files with missing lines	Patch %	Lines
src/multio/mars2mars/Rules.cc	0.00%	209 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #245      +/-   ##
===========================================
- Coverage    55.81%   55.28%   -0.53%     
===========================================
  Files          325      325              
  Lines        21319    21525     +206     
  Branches      1681     1683       +2     
===========================================
+ Hits         11900    11901       +1     
- Misses        9419     9624     +205     

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