[PyTorch] Support ExclusivelyOwned<caffe2::Tensor> (#81964)
Since `caffe2::Tensor` also shares `TensorImpl`, we can apply `ExclusivelyOwned` to it as needed.
Differential Revision: [D38066340](https://our.internmc.facebook.com/intern/diff/D38066340/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81964
Approved by: https://github.com/ezyang
