The enum changes should work on PyQt 5.x, and are required in PyQt 6.x.
They are not supported by the PyQt5 typings however, so we need to run
our tests with PyQt6.
- changes can now be undone
- the same field can now be mapped to multiple target fields, allowing
fields to be cloned
- the old Qt dialog has been removed
- the old col.models.change() API calls the new code, to avoid
breaking existing consumers. It requires the field map to always
be passed in, but that appears to have been the common case.
- closes#1175
