CPAlgorithms: refactor the object cutflow

This is the same as !68554 (merged), which was reverted due to a mismatch in the sequences leading the CI to crash in other MRs (but not !68554 (merged) ??). So here I also fix the sequences and hopefully no more crash

PhysicsAnalysis/Algorithms/AsgAnalysisAlgorithms/AsgAnalysisAlgorithms/ObjectCutFlowHistAlg.h

 /*
-  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 */
 
 /// @author Nils Krumnack
+/// @author Baptiste Ravina
 
 
 #ifndef ASG_ANALYSIS_ALGORITHMS__OBJECT_CUT_FLOW_HIST_ALG_H
@@ -11,7 +12,6 @@
 #include <AnaAlgorithm/AnaAlgorithm.h>
 #include <AsgTools/PropertyWrapper.h>
 #include <SelectionHelpers/ISelectionNameSvc.h>
-#include <SelectionHelpers/ISelectionReadAccessor.h>
 #include <SelectionHelpers/SysReadSelectionHandle.h>
 #include <SystematicsHandles/SysReadHandle.h>
 #include <SystematicsHandles/SysListHandle.h>
@@ -19,19 +19,14 @@
 
 namespace CP
 {
-  /// \brief an algorithm for dumping the kinematics of an IParticle
-  /// container into histograms
-  ///
-  /// This is mostly meant as a temporary helper algorithm to debug
-  /// the common CP algorithms as they get developed.
+  /// \brief an algorithm for dumping the object-level cutflow
 
   class ObjectCutFlowHistAlg final : public EL::AnaAlgorithm
   {
     /// \brief the standard constructor
   public:
     ObjectCutFlowHistAlg (const std::string& name, 
-                            ISvcLocator* pSvcLocator);
-
+			 ISvcLocator* pSvcLocator);
 
   public:
     StatusCode initialize () override;
@@ -44,10 +39,10 @@ namespace CP
   private:
     SysListHandle m_systematicsList {this};
 
-    /// \brief the jet collection we run on
+    /// \brief the particle collection we run on
   private:
     SysReadHandle<xAOD::IParticleContainer> m_inputHandle {
-      this, "input", "", "the input collection to run on"};
+      this, "input", "", "the input particle container to run on"};
 
     /// \brief the preselection we apply to our input
   private:
@@ -66,13 +61,10 @@ namespace CP
   private:
     Gaudi::Property<std::string> m_histTitle {this, "histTitle", "object cut flow", "title for the created histograms"};
 
-
-  private:
-    std::vector<std::string> m_selection;
-
-    /// the list of accessors and cut ignore list
+    /// \brief the input object selections for which to create a cutflow
   private:
-    std::vector<std::pair<std::unique_ptr<ISelectionReadAccessor>,unsigned> > m_accessors;
+    SysReadSelectionHandleArray m_selections {
+      this, "selections", {}, "the inputs to the object cutflow"};
 
     /// \brief the total number of cuts configured (needed to
     /// configure histograms)