Adding PLV isolation WPs

Following the discussion in MR 26957, I've re-created this new MR. The primary aim of this update is to simply add PLVLoose or PLVTight isolation WPs, which are BDT-based isolation WPs. Basically we cut on PromptLeptonVeto score, which can be calculated and augmented at derivation level. The trouble is that, for low-pt leptons, we now use new BDT score, LowPtPLV. This score is currently not calculated at derivation level, therefore we are trying to augment the score in IsolationSelection package.

• Presentation about the final WP definition and its performance -> 30th Sep. IFF meeting
• Discussion on LowPtPLV -> 16th Sep. IFF meeting