Update of Truth Rivet Tool

Oleh Kivernyk requested to merge okiverny/athena:TruthRivetTools-myBranch into 21.2

Added the Stage-1.1 and Stage-1.1-Fine versions of STXS classification: https://twiki.cern.ch/twiki/bin/view/LHCPhysics/LHCHXSWGFiducialAndSTXS#Stage_1_1 The old Stage-1 classification is not affected.

Also implemented the bugfix for ttH in the STXS classification tool spotted by RD Schaffer.

This is used in the derivation release.

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