PowhegControl: fixing reweighting issues
requested to merge atlas-physics/pmg/mcexperts/powheg-experts/athena:21.6-PowhegReweightingIssues into 21.6
This MR should fix some of the problems for PowhegControl seen in AGENE-2047
The (xml-)reweighting was eventually failing because the clobberlhe (and some of the rwl_) keyword was not exposed in some V2 processes. I checked all of them and added the keywords where they were missing.