Fix torch.{unique, unique_consecutive} out of bound (#71540)
Summary:
This PR ensures that the input iterator is always in front of the output
iterator. Thus, we won't have a out of bound issue since the input
iterator will meet the end before output iterator meets.
Fixes https://github.com/pytorch/pytorch/issues/71089
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71540
Reviewed By: mruberry
Differential Revision: D33688123
Pulled By: ngimel
fbshipit-source-id: f57718931d09a0fbea76ac1bd6cc8c7150af0978
(cherry picked from commit dc6e0e219a9e9b9ccea9ff5406458b56f556b2e4)
