DataModelAthenaPool+TPTools: Cleaning up converters for MT thinning.
Add const converter interfaces. Add interfaces for passing thinning caches to converters. General clean up.
Slight cleanup for TPConverterConstBase and TPCnvStdVectorConst.
Add const converter interfaces. Add interfaces for passing thinning caches to converters. General clean up.
Slight cleanup for TPConverterConstBase and TPCnvStdVectorConst.