Revert "Remove some unnecessary <iostream> includes from headers (#106914)"
This reverts commit 60936e4c296e79f56cac2431a560970bb4529d03.
Reverted https://github.com/pytorch/pytorch/pull/106914 on behalf of https://github.com/ZainRizvi due to Sorry, but this is breaking internal builds. Seems like a lot of internal code depends on some of the removed imports ([comment](https://github.com/pytorch/pytorch/pull/106914#issuecomment-1688605975))
