Fix compiler warnings in Athena
There are quite a few warnings when we compile in Athena, e.g.
In file included from /afs/cern.ch/user/d/dguest/afswork/dumper/training-dataset-dumper/BTagTrainingPreprocessing/src/H5FileSvc.cxx:1:
/afs/cern.ch/user/d/dguest/afswork/dumper/training-dataset-dumper/BTagTrainingPreprocessing/src/H5FileSvc.h:13:7: warning: 'class H5FileSvc' derives directly from 'Service'; should derive from 'AthService' instead and use its methods
13 | class H5FileSvc : public virtual Service
| ^~~~~~~~~
we should fix these and then enable -Werror
or something so they can't come back.