22.0-redundant_code_removal-InDetPhysValMonitoring
In the context of ATLIDTRKCP-255, and having introduced unit tests to ensure functioning. This MR removes redundant legacy code, in particular:
- Plain text (.hdef) file definition as input to the HistogramDefinitionSvc
- The unused Xerces-SAX event driven parser (only the DOM one is used)
- Unused test code, since replaced by the unit tests