First pieces of larger merging of HTT Simulation (Trigger/TrigHTT) into athena/master
This is a first MR to replace !50718 (closed), which may be too big to do all in one bunch. The pieces in this MR are the few core pieces of the old HTT simulation code that do not have any other dependencies in the HTT framework. This is to be discussed at next week's upgrade SW integration meeting, but we thought it would be helpful to have this MR already in place before then. We have a plan to break the above single MR into 2-3 additional pieces after this one.