Draft: Offshell branch merge

These are a few changes from the offshell development branch that we'd like to merge with master. This is mostly to align with https://gitlab.cern.ch/atlas-physics/higgs/hww/HWWAnalysisCode/-/merge_requests/961 on HWWAnalysisCode, having all offshell developments in the respective master branches and thus also not needing to point to a different commit in the CAFCore submodule on HWWAnalysisCode master for the offshell changes to as intended.

It is in draft status since it seems some test related to plotting with the TQHWWPlotter is failing, it may very well be that there was indeed a change induced by the first commit that causes the plot to look slightly different. But before diving into this I wanted to confirm if this is something that we would need to fix, given that this plotter is deprecated?