Allow to take into account grand parents in ClusterEfficiency algorithm

Use grandparents to allow selection of pi0 when running ClusterEfficiency.

This MR is required for a Moore MR Moore!1498 (merged) that implements new calo efficiency counters based on pi0.

The code was developed by @aszabels. I've rebased it on master and updated where needed.

Calo/CaloAssociators/src/CaloClusterEfficiency.cpp

@@ -110,9 +110,14 @@ namespace LHCb::Calo::Algorithms {
         // select signal as defined by m_PDGID and m_PDGIDParent
         if ( !mcp ) continue;
         if ( mcp->particleID().pid() != m_PDGID ) continue;
-        if ( !mcp->mother() || abs( mcp->mother()->particleID().pid() ) != m_PDGIDParent ) continue;
+        auto mcp_mother = mcp->mother();
+        if ( !mcp_mother || abs( mcp_mother->particleID().pid() ) != m_PDGIDParent ) continue;
+        if ( m_PDGIDGrandparent &&
+             ( !mcp_mother->mother() || abs( mcp_mother->mother()->particleID().pid() ) != m_PDGIDGrandparent ) )
+          continue;
         if ( msgLevel( MSG::DEBUG ) )
-          debug() << "MC particle and parent ID are: " << m_PDGID << ", " << m_PDGIDParent << endmsg;
+          debug() << "MC particle, parent and grandparent ID are: " << m_PDGID << ", " << m_PDGIDParent << " and "
+                  << m_PDGIDGrandparent << endmsg;
 
         // apply min ET cut
         if ( mcp->pt() < m_minET ) continue;
@@ -220,6 +225,7 @@ namespace LHCb::Calo::Algorithms {
     // properties
     Gaudi::Property<int>   m_PDGID{this, "PDGID", 22};
     Gaudi::Property<int>   m_PDGIDParent{this, "PDGIDParent", 511};
+    Gaudi::Property<int>   m_PDGIDGrandparent{this, "PDGIDGrandparent", 0};
     Gaudi::Property<float> m_minMCfraction{this, "minMCfraction", 0.9};
     Gaudi::Property<float> m_minMatchFraction{this, "minMatchFraction", 0.9};
     Gaudi::Property<float> m_minET{this, "minET", 50.};