Remove iterativeConeGenJets from CMSSW, Add GenJetsNoNu to RECO/AOD

Two long outstanding issues addressed in this pull request:
- Remove iterativeCone6GenJets from RECO+HLT
- Prepare switch from ak4GenJets to ak4GenJetsNoNu in RECO+AOD
Discussed at JMAR meeting:
https://indico.cern.ch/event/357182/contribution/5/material/slides/0.pdf
After a more general presentation, to discuss the change, but before the last 7_4_X pre-release, we would like to remove the ak4GenJets collection, together with the other jet collections discussed at the RECO meeting today.
https://indico.cern.ch/event/354427/session/4/contribution/8/material/slides/0.pdf

Details:
- Add ak4GenJetsNoNu and ak8GenJetsNoNu and remove iterativeCone5GenJets from RECO+AOD
- HLT jet validation use now ak4GenJets instead of iterativeCone5GenJets as truth reference.
- Remove genMetIC5GenJets, genMetCaloAndNonPrompt.
- PAT is not yet touched and ak4GenJets are kept for a pre-release cycle because it needs new RelVals before changes are possible and ak4GenJets can be dropped
is the  size 5 here on purpose, or was the remaining IC5 an incomplete migration to size 4?
If the latter, we should be using ak4GenJets here, right?