TrigMessageSvc: Implement monitoring histograms
Add back the same monitoring histograms for the message statistics as we had in release 21. Remove some obsolete properties. This closes ATR-19394.
Notes:
- I tried using the "Monitored" infrastructure for this but since the MessageSvc is constructed as one of the first services, one has to be extremely careful what other components to use (e.g. even the CHECK macros are problematic). In the end I decided it wasn't worth the trouble and reverted back to just registering histograms directly with the THistSvc.