Validate histogram output in reference comparisons

As part of reference comparisons we should be testing that histogram output is stable. The minimum is number of entries, and some moments (mean, rms, etc.), but we could also consider recording all the bin data.

Currently the default MessageSvcSink does not print anything for histograms. That's addressed in gaudi/Gaudi!1320

Another way to monitor histogram output is gaudi/Gaudi!1362 (merged) , which started being used in Rec!3083 (diffs) .

We need to make decide and settle on a common way to do things (i.e. meaningful defaults and recipe for how to do more).

See discussion at Rec!3074 (comment 5962375)

mentioned in merge request Rec!3074 (merged)

As mentioned in Rec!3074 (comment 5963486), according to this code : https://gitlab.cern.ch/gaudi/Gaudi/-/blob/master/GaudiCoreSvc/src/MessageSvc/MessageSvcSink.cpp#L176, the default MessageSvcSink should print something for histograms. And according to https://gitlab.cern.ch/gaudi/Gaudi/-/blob/master/GaudiCoreSvc/src/MessageSvc/MessageSvcSink.cpp#L40, it should be very similar to counters with only the number of entries reported.

I'll investigate

ok, the problem was dead simple... in https://gitlab.cern.ch/gaudi/Gaudi/-/blob/master/GaudiCoreSvc/src/MessageSvc/MessageSvcSink.cpp#L176

      if ( std::string_view( ent.type ).substr( 0, 8 ) == "counter:" || ent.type == "statentity" ||
           ent.type == "histogram" ) {

it should have been

      if ( std::string_view( ent.type ).substr( 0, 8 ) == "counter:" || ent.type == "statentity" ||
           std::string_view( ent.type ).substr( 0, 9 ) == "histogram" ) {

My bad, it has been wrong from the beginning according to git. Let me try to fix it and see the consequences...