Make Pileup reweighting optional, harmonise with year string
At the moment, pileup reweighting is always performed: https://gitlab.cern.ch/HiggsDNA-project/HiggsDNA/-/blob/master/higgs_dna/workflows/base.py#L227 However, it would be beneficial if this were not the case. For example, sometimes we might want to perform studies where the pileup weight is not applied in order to study the raw weight distribution from MC.
Therefore: We should add a flag to make pileup reweighting optional. We should consider the pileup reweighting as a nominal correction (perhaps we should also add systematic for this, is this possible?). Additionally, we probably want to harmonise with the newly added "year" string to allow for pileup reweighting of different periods/years. We could include pulling the JSONs for LUM POG from JSONPOG-integration from here: https://gitlab.cern.ch/cms-nanoAOD/jsonpog-integration/-/tree/master/POG/LUM To allow for Run 2 reweighting (relevant for Tiziano et. al., perhaps?)