main MRs important for AthGeneration: update PowhegControl interface to the version from rel. 21.6, some fixes to Herwig7 common fragments https://gitlab.cern.ch/atlas/athena/-/merge_requests/41433 include Rivet in the AthGeneration build https://gitlab.cern.ch/atlas/athena/-/merge_requests/41444 PowhegControl corrections required by Python3 https://gitlab.cern.ch/atlas/athena/-/merge_requests/41709