Join issue

See [here](https://sdmx-twg.github.io/vtl/v2.1/reference_manual/operators/Join%20operators/Join/index.html#additional-constraints).

Duplicated column name does not throw error in Trevas.

"Components whose names are of the form “alias1#c1” and “alias2#c1” in the structure of the virtual Data Point, since the removal of “alias1” and “alias2” would cause the clash. If, after the aliases removal two Components have the same name, an error is raised"