Remove most of the `===DONE===` tags and its variations. Keep `===DONE===` if the test output otherwise becomes empty. Closes GH-4872.
- bugfix #27063 - bugfix #27929 - bugfix #28099 - bugfix #28125 # The amount of code is needed to solve the return by reference problem. # dual_it and derived also need their own iterator handlers to be able # to return by reference.