SLB: Add MVA-based isolation
The SLB group have developed BDT-style MVAs to decide on which extra pions may be kept for reconstructing excited states (e.g. D*). This is still WIP, but preliminary tests on one line (spruce_bptod0taunu_d0tokpipipi_tautopipipinu_line) show that sprucing bandwidth may be reduced by approximately 50% by using this MVA rather than using persist_reco = True with ~98% signal efficiency for decays such as B->D* l nu.
This MR is dependent on: Rec!3550 (merged), !3206 (merged) and lhcb-datapkg/ParamFiles!81 (merged)
This work in collaboration with: @chinghua @dovombru @vekirseb @amathad @jugarcia @sutclifw @groberts @masmith
A recent set of slides showing this working can be seen: https://indico.cern.ch/event/1403138/contributions/5898884/attachments/2832281/4948740/isoTools_update_05.04.24.pdf