Add AsgPriorityDecorationAlg
Add AsgPriorityDecorationAlg which is meant to decorate Overlap Removal priorities (and potentially for other clients, so no OR in the name). It loops over different preselections and decorates priorities provided. Default (lowest) is 0.
Also fix an unspotted typo in Athena definitions.
Tagging also @omajersk and @mrimoldi to confirm I got the point of OR priorities. An example usage is here: https://gitlab.cern.ch/tadej/MultiLeptonAnalysis/-/blob/next/MultiLeptonAlgs/python/Algs/Postprocessing.py#L23-27