Add the possibility to save event run number

Add the possibility to save the run number of events.

This could be useful for debugging to identify an event as (eventNumber, runNumber) uniquely identify an event

Tagging @npond, @dguest and @alfroch, please let me know if you have comments thanks

PS: I did not edited the json files to save that info as default as this is I guess mainly for debugging and is not needed for usual transformer training