Wrap usage of truth barcode as a unique ID - part 1 (ATLASSIM-6978)
In code where the truth particle/vertex barcode is only used in checks that it is identical to another barcode value, then the barcode calls can be wrapped using the HepMC::uniqueID(const T& p) templated helper function.
The idea here is to separate out the different conceptual usages of barcode ahead of its removal/replacement with id and the revised status scheme. See ATLASSIM-6906 for more details.