[PyTorch] Update expand_outplace API to match expand_inplace (#55245)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55245
Like `expand_inplace`, `expand_outplace` now returns
`MaybeOwned<Tensor>` in most cases. I wasn't confident around the
ownership semantics of the `TensorList` -> `std::vector<Tensor>` case, so I
left that one alone.
ghstack-source-id: 126170052
Test Plan: Existing CI.
Reviewed By: ezyang
Differential Revision: D27522811
fbshipit-source-id: 28c5a626b65681e361f4006a0aaa7dc23ba9612a
