new pileup handling

[pinkenburg]

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work for users)
• [ ] Requiring change in macros repository (Please provide links to the macros pull request in the last section)
• [x] I am a member of GitHub organization of sPHENIX Collaboration, EIC, or ECCE (contact Chris Pinkenburg to join)

What kind of change does this PR introduce? (Bug fix, feature, ...)

The pileup will from now on be given in kHz to accommodate multiple different pileup scenarios. The old pileup where a parameter set a hardcoded scenario is still here but will be phased out. This is not checked by jenkins, no need to run it [skip-ci]

TODOs (if applicable)

Links to other PRs in macros and calibration repositories (if applicable)