Add a few EPOS4 configurations

[jackal1-66]

EPOS4 physics generation always happens internally in the symmetric nucleon-nucleon CM frame. hepmc_rapcms does not change that internal physics, but it applies a rigid rapidity boost (dy = -hepmc_rapcms, applied in src/KW/out.f → fillhepmc) to every particle written to output, which means re-expressing the same collision in the lab frame. This is here used for pO and should be used for p-Pb as well (the shift there is 0.465, from the same Δy = 0.5·ln(E_p/E_target-per-nucleon formula).

[github-actions]

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[victor-gonzalez]

@jackal1-66, thank you!!
I left a few suggestions in case you want to consider them

[victor-gonzalez]

I would suggest to either rename the optns files in config/examples/epos4/generator to incorporate hydro when appropriate or copy to config/common/epos4/generator the corresponding files from config/examples/epos4/generator renamed to incorporate hydro

[jackal1-66]

Ciao @victor-gonzalez thank you for your comments. I changed the description in the headers, however I didn't implement your change into the rapidity boost, as it seems to be incorrect. I ran some additional tests and put a more precise value. I will rename and move in common the files in the example folder in a second moment with a dedicated PR and follow the "_hydro" standard that I set in this PR. For now I would try to put these configurations in so that we can test them in HY.