Reorganising TriggerEDM code

I've started to reorganising the TriggerEDM code to have:

• a separate file for Run 2 with just the lists of containers, named TriggerEDMRun2.py
• a separate file for all functions that are used across the ATLAS code, called TriggerEDM.py (name stayed the same to not have to modify many functions)
• started adjusting some functions in TriggerEDM.py to be able to deal with Run 3 EDM.

The only change that would require changes in subsequent packages is I think renaming the TriggerHLTList to TriggerHLTListRun3 in TriggerEDMRun3.py, this has been done as to not confuse things, but can be reverted and imported in the TriggerEDM.py under this name only if there are preferences. This change would mean that I have to fix the name in these places, which I haven't done yet in this MR: https://acode-browser.usatlas.bnl.gov/lxr/search?%21v=head&_filestring=&_string=TrigEDMConfig.TriggerEDMRun3 (8 occurrences in the packages RecJobTrasforms (3), TrigUpgradeTest (2), TriggerJobOpts (3 times in one file)) ==> this has been done now

For the other change regarding the move of the Run 2 EDM lists to TriggerEDMRun2.py: because these lists are imported in the TriggerEDM.py, any imports requested from TriggerEDM of these lists in older code should still work.

Once the reorganisation is done, I'll work further on the implementation of adding/removing dynamic variables for Run3.

Documentation and discussion can also be found in ATR-20095.

Tagging @okuprash, @tbold, @tamartin, @stelzer, @wiedenma, @smh, @fwinkl for comments and raising potential problems with this.