Added emulator tool

[cducher]

This PR contains the Atlas emulator tool implementation, which makes use of the GRIB reader reviewed in this PR.
/!\ there is a parallelisation bug in the paramBuffer broadcast of the GRIB reader, so running with 3, or 5+ processes do not work at the moment. You can try this emulator with 1,2, or 4 processes at the moment.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 67 lines in your changes missing coverage. Please review.

Please upload report for BASE (feature/nwp-emulator-grib-source@2527575). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/nwp_emulator/nwp_emulator.cc	0.00%	65 Missing ⚠️
src/nwp_emulator/nwp_data_provider.cc	0.00%	2 Missing ⚠️

Additional details and impacted files

@@                         Coverage Diff                         @@
##             feature/nwp-emulator-grib-source       #4   +/-   ##
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  Coverage                                    ?   29.46%           
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  Files                                       ?       49           
  Lines                                       ?     1972           
  Branches                                    ?      138           
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  Hits                                        ?      581           
  Misses                                      ?     1391           
  Partials                                    ?        0           

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