Allow adding extra trigger collections to EDM via preExec

This is to allow easy production of private samples or of samples for detailed temporary validation of trigger, without adding the temporarily needed collections to the (persistent) trigger EDM list.

An example pre-exec to store new collections/variables:

runArgs.preExec = ['from AthenaConfiguration.AllConfigFlags import ConfigFlags;ConfigFlags.Trigger.ExtraEDMList=[(\'xAOD::BTaggingAuxContainer#HLT_BTaggingAux.DL1r_pc\',          \'BS ESD AODFULL AODSLIM AODVERYSLIM\', \'Bjet\'), (\'xAOD::TrigBphysContainer#HLT_DimuEF\',                                 \'BS ESD AODFULL AODSLIM AODVERYSLIM AODBLSSLIM\', \'Bphys\'), (\'xAOD::TrigBphysAuxContainer#HLT_DimuEFAux.\',                          \'BS ESD AODFULL AODSLIM AODVERYSLIM AODBLSSLIM\', \'Bphys\') ];']

For now it works for Run 3 EDM only. The format of the list to add is the same as in TriggerEDMRun3.py.

Tested by removing single varialbe DL1r_pc (belongs to HLT_BTaggingAux.) and collections HLT_DimuEF, HLT_DimuEFAux. from EDM, and adding them back via the preExec above, using test_trigAna_RDOtoAOD_v1Dev_build.py.

Tagging @jburr, @jmasik, @tbold, @tamartin.