Implement pools chaining via TChain + example and test macro

[jackal1-66]

Multiple things will be changed by this PR in the usage of the event pools:

• The pools are now chained so that when all the events are used in a file, another file will be pulled → no more repeated files when randomisation is enabled
• The development is a first step to use event pools on hyperloop
• Both an example and the test macro were implemented
  Fixes implemented along the way:
• RoundRobin not considered when using evtpools → now it is forwarded and the events are reused in case all the files have been opened and completely used
• The driver seed was being thrown away → with rngseed = 0 (the default) the generator called gRandom->SetSeed(0), discarding the driver seed. Now with 0 the seed is taken directly from o2-sim