Field.rel is now deprecated. Rel objects have now also remote_field attribute. This means that self == self.remote_field.remote_field. In addition, made the Rel objects a bit more like Field objects. Still, marked ManyToManyFields as null=True.
model_options
And moved `tablespaces` option tests to it. The new folder can be used to test models/options, like the new option added in refs #22778.