[PWGLF] Omega(2012): shared selection core, Xi(1530)K mode and ML training-table exporter

Move the Xi, K0s and track selection and the candidate enumeration of the
Omega(2012) analysis into PWGLF/Core/Omega2012AnalysisCore.h with hooks for
the task histograms, in the same way as the K1 core. The two decay modes
are analysed separately throughout: Omega(2012)- -> Xi- K0S (unchanged
histogram output) and Omega(2012)- -> Xi(1530)0 K- -> Xi- pi+ K-. The
previous three-body code combined Xi + pi + K0S, which cannot be an
Omega(2012)- by charge, and is removed; the new mode uses a charged kaon
track selected with ResoAnalysisSelectionCore, with wrong-sign controls
kept apart from the signal pattern.

Add the per-mode feature contracts (Omega2012MlFeatures.h), the derived
tables (LFOmega2012MlTables.h) and the omega2012-training-table workflow
that writes the candidates of each mode, their features, pass bits and MC
truth, plus a generated-parent audit by decay channel.

Author: BongHwi