CA: make the ideal hit producer run with the event builder

Reset the hit indices in CbmEvents when the hits are rebuilt by the CaIdealHitProducer. I am making @v.friese a reviewer since I have added an additional cleaning method to CbmEvent.

@v.friese, I'll merge this MR because it is urgently needed for the analysis. Still, please review it later. We can revert the changes if you don't like them.