23.0-cppcheck-TrigInDetAnalysisUser

Address clang 15 compiler warnings about unused variables contributing to ATLASRECTS-7430. Solve cppcheck warnings, various ranging from warnings (no user copy/assignment on classes which manage resource – I've explicitly deleted these); uninitialised members in a copy constructor, various minor performance defects concerning string self-assignment of substring, now replaced by resize. tagging @averbyts