Replace const HepMC::GenParticlePtr with HepMC::ConstGenParticlePtr

This is just a small set of changes to ensure that the meaning of some lines isn't changed by the switch to using the HepMC::GenParticlePtr typedefs (part of the preparation for the HepMC3 migration).

For HepMC2

const HepMC::GenParticlePtr == HepMC::GenParticle* const
HepMC::ConstGenParticlePtr == const HepMC::GenParticle*

FYI @averbyts

This merge request affects 11 packages:

• Generators/EvgenProdTools
• Generators/EvtGen_i
• Generators/FlowAfterburner
• Generators/GeneratorObjects
• Generators/GeneratorObjectsTPCnv
• Generators/Rivet_i
• Reconstruction/MissingETEvent
• Simulation/FastSimulation/FastSimulationEvent
• Simulation/G4Atlas/G4AtlasTests
• Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimParametrization
• Simulation/Tools/CaloSamplingFractionAnalysis

Adding @goetz ,@jchapman ,@pjacka ,@mfauccig ,@xiaozhon ,@ahasib ,@vpascuzz ,@tadej ,@schaarsc as watchers

added Generators JetEtmiss Reconstruction Simulation master review-pending-level-1 labels

CI Result SUCCESS (hash 41c87616)

	Athena	AthSimulation	AthGeneration	AnalysisBase
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 19270]

changes look fine, tests pass, L1 approving.

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit 94634975

added sweep:ignore label