TriggerJobOpts: move GapFiller to reconstruction stage

Move the "GapFiller" to the reconstruction stage for the bulk of the EDM collections. The setup is now:

Online:

• View-merging
• Fix collections links and Gap-filling of the decision container (TrigComposite)

Offline:

• Gap-filling of the main EDM collections

Also remove the HLTEDMCreator.LateEDMKeys property as the same can be achieved by not populating the collection properties with these keys in the first place.

Relates to ATR-27986.

cc @tamartin @khoo