Xi02ppi and Xim2lambdapi run 2 selection (supersedes !810)

Selections for \Delta S = 2 hyperon decays. Currently including Xi0 -> p+ pi- for signal MC, the run 2 BHadroncompleteevent stream, as well as the run 2 Charm stream from the 2023 re-stripping, which completed in Jan 2024. Also including the the Xi- -> Lambda0 pi- normalisation channel for the Charm stream of the 2023 re-stripping. The superseded ntuples from !810 (merged) can be deleted after the MR is finalised.