Add aliases to TruthPArticle methods so the TruthPArticle can be used with the...

Merged Andrii Verbytskyi requested to merge averbyts/athena:compatibility_with_hepmc into 23.0

Add aliases to TruthPArticle methods so the TruthPArticle can be used with the same templated functions as HepMC:GenParticle

Tag @jchapman @pclark

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