Add file content comparison to the test

This adds an automated comparison of the file content e.g.

============ Compare file content:
Present only in AOD made with CA, and not in ref (old-config):
METMap_Truth
MET_Calo
MET_EMTopo
MET_EMTopoRegions
MET_LocHadTopo
MET_LocHadTopoRegions
MET_Track
MET_Truth
MET_TruthRegions
MSOnlyExtrapolatedMuonsLRTTrackParticles

Present only in ref (old-config), not in AOD made with CA:
AFPProtonContainer
AFPSiHitsClusterContainer
AFPToFTrackContainer
AFPTrackContainer
AFPVertexContainer
DiTauJets
ElectronCaloRings
ElectronRingSets
MSDisplacedVertex
MSOnlyExtraPolatedMuonsLRTTrackParticles
MSonlyTracklets
MuonTruthParticles
MuonTruthSegments
StauSegments

so in other words, this should hopefully replicate the work done by @elmsheus in his CA comparison emails.

edit: I forgot to say that I didn't add an art-result to this, because I didn't want to change the existing numbering, and wanted to discuss it. And also we know it will just fail for now. But I'm happy to add it if requested...

cc @elmsheus @nstyles