Revert "[Dynamo] Remove cross import in dynamo unit tests (#100851)"
This reverts commit c4bbeb5b8a27259fc2b644e3f185b4ba859a2d39.
Reverted https://github.com/pytorch/pytorch/pull/100851 on behalf of https://github.com/jeanschmidt due to breaking internal builds ([comment](https://github.com/pytorch/pytorch/pull/100851#issuecomment-1540646623))
