[ATR-28717] Hook Run4 EDM file in to TriggerEDM.py
This change allows the content of the TriggerEDMRun4 file to be returned for R4 MC.
This is currently in addition to TriggerEDMRun3, and will supersede any entries listed there as well with the same SG key.
This MR is going to 24.0 as it touches common code (TriggerEDM.py) which we don't want to let diverge.
cc @cantel