Revert "Avoid COW materialization in `at::parallel_for/parallel_reduce` (#120455)"
This reverts commit cabc09a5f259f1cc1e3bad1d80b5e5274838bced.
Reverted https://github.com/pytorch/pytorch/pull/120455 on behalf of https://github.com/izaitsevfb due to breaks xla jobs ([comment](https://github.com/pytorch/pytorch/pull/120455#issuecomment-1970026100))
