CMSSW_12_4_20

Changes since CMSSW_12_4_19:

CMSSW_12_4_19...CMSSW_12_4_20

• #44607 from @menglu21: update ReweightUserHooks.h in CMSSW_12_4_X generators
• #44420 from @lauridsj: [Backport 12.4.X] Update Pythia Hook for BB4L generators
• #44269 from @forthommel: [12_4_X] CepGen generator interface generators
• #43899 from @Dr15Jones: Issue exception for ROOT file forward incompatiblity problem [12_4] core
• #43692 from @Dominic-Stafford: Add relval for Herwig Matchbox generators pdmv upgrade

CMSDIST Changes between Tags REL/CMSSW_12_4_19/el8_amd64_gcc10 and REL/CMSSW_12_4_20/el8_amd64_gcc10:

cms-sw/cmsdist@REL/CMSSW_12_4_19/el8_amd64_gcc10...REL/CMSSW_12_4_20/el8_amd64_gcc10

• cms-sw/cmsdist#9040 from @forthommel: [12_4_X] Added cepgen 1.2.1patch1 to standard CMSSW tools
• cms-sw/cmsdist#9013 from @tvami: [12_4_X] Update EvtGenInterface to V02-09-00
• cms-sw/cmsdist#9007 from @cms-sw: [12_4_X] Cherry-pick ROOT fixes for forward compatibility
• cms-sw/cmsdist#8930 from @Dominic-Stafford: [12.4.X] Add Collier package and use ninja from gosamcontrib for madgraph