[SPMD] Introduce remove_copy_for_optimizer optimization (#98580)
This PR adds the ability to remove unused `copy_` (`len(node.users) == 0`) that generated by tracing the optimizer.
Differential Revision: [D44761556](https://our.internmc.facebook.com/intern/diff/D44761556/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/98580
Approved by: https://github.com/mrshenli
