Add VBS samples

[amecca]

This add the samples used by VBS to the common CSV files. Note that the primary dataset is different between 2022/23 (ZZto4L-2Jets_...) and 2024 (ZZJJto4L-...). The cross sections are taken from XSDB.
Not sure if the settings APPLY_K_... need to be used.

[namapane]

Thanks @amecca. The flag APPLY_K_NNLOQCD_ZZQQB specifies that NNLO/NLO QCD k-factors for qqZZ have to be applied (they will be stored as specific variables and are multiplied to overallEventWeight). These are needed for the qqZZ POWHEG sample which is generated at NLO. As of now, these are the k-factors derived for Run 2.
I don't know the details of these MADGRAPH "EW/QCD" samples but my guess is that these k-kfactors are probably not the correct ones for these samples, but please check with experts.

APPLY_K_NLOEW_ZZQQ is intended to specify that EW k-factors should be applied as well, but we don't have these implemented right now, so the card does nothing for the time being. In Run2, this k-factor was !=1 only above 200 GeV or so. We will need to update these k-factors for whatever results covering the high mass region with the qqZZ POWHEG sample. Also in this case, I don't know if the same factors would then apply to these MADGRAPH "EW/QCD" samples, but if I have to guess I would say no - experts may know better.

Some progress in updating these k-factor has been discussed recently (see here).

Let me know if you wanty to merge this PR as is or if you prefer to collect more info on whether these k-factors are better included or not.

Also a small comment, can you please add to the comment lines [eg here] a reference of where the XS*BR comes from? In the PR description it's specified ("The cross sections are taken from XSDB.") but after a few months it becomes hard to figure out, or check if the numbers are up to date (this is the case for most XSs we have in these files unfortunately). A direct link would be best if possible.