CMSSW_9_3_19

Changes since CMSSW_9_3_18:

CMSSW_9_3_18...CMSSW_9_3_19

• #29538 from @Dominic-Stafford: Herwig7.2 upgrade 9 3 generators

• #29356 from @menglu21: Update BasicGenValidation_cff.py dqm generators

CMSDIST Changes between Tags REL/CMSSW_9_3_18/slc6_amd64_gcc630 and REL/CMSSW_9_3_19/slc6_amd64_gcc630:

cms-sw/cmsdist@REL/CMSSW_9_3_18/slc6_amd64_gcc630...REL/CMSSW_9_3_19/slc6_amd64_gcc630

• cms-sw/cmsdist#6681 from @SiewYan: [9_3_X] upgrade sherpa to 2.2.11
• cms-sw/cmsdist#6475 from @Dominic-Stafford: Upgrade Herwig to v7.2.1, and add patch to fix crash when reading lhe
• cms-sw/cmsdist#5774 from @Dominic-Stafford: Upgrade Herwig 7.1.4 to Herwig 7.2.0
• cms-sw/cmsdist#5687 from @cms-sw: [9.3.X][FrontierClient] Update to verison 2.9.1