Update Pvertexer for ALICE3 purposes

[njacazio]

@shahor02 @ginnocen I produced some prototype for the vertexing to use in O2 with ALICE3, the implementation in DelphesO2 is here https://github.com/preghenella/DelphesO2/pull/36.
@shahor02 I followed your suggestions.
Of course it would be useful if we could discuss the details of the implementation, in particular concerning the timestamp parameters, for that I would need your blessing.
I can produce few performance plots to check that everything is consistent.

[shahor02]

Hi @njacazio
I don't think this will work: you are creating a pool of tracks with the same dummy min/max timestamp [0:1]. As a result the time and Z clustering done before the vertexing will lead to 1 huge time cluster and all vertices will pile-up together. But Alice3
I am anyway planning to change the input from TrackTPCITS to templated tracks with TrackParCov + TimeStampWithError functionalities.
I can also change the gsl::span<const o2::ft0::RecPoints> ft0Data to span of T providing T.getInteractionRecord() method (the only one used in validation). Then, you can even provide a dummy vector, instead of cloning these methods.
Let me know if this is ok.

[njacazio]

Hi @shahor02 thanks a lots for the feedback, this is what I needed. Indeed your solution would be the cleanest, thanks a lot!