Modernize copy prevention in basic/ComparingTracer and MessageListenerFactory (#673)
Two related cleanups in `basic/`:
**`ComparingTracer.hh`**: Replace private-and-undefined copy constructor
with public `= delete`; also explicitly delete copy assignment. The
`std::fstream` member already makes copies impossible, but `= delete`
documents the intent at the class level.
**`mpi/MessageListenerFactory.hh`**: Remove the redundant
private-undefined copy constructor and copy assignment.
`MessageListenerFactory` inherits from
`utility::SingletonBase<MessageListenerFactory>`, which already deletes
both copy operations — the manual declarations were dead code.