TriggerMenuMT: Additional check on event building and streaming consistency
Reorganise slightly the PartialEventBuildingChecks
in menu_config_tests.py
to include one more
streaming check. Namely, ensure that all full-event-building chains are streamed only to
full-event-building streams. In other words, that a partial event building stream doesn't include
a full-event-building chain by mistake.
Also update the definition of the special "DISCARD" stream to comply with the newly enforced requirement.
Closes ATR-22242