[DataLoader2] Change serialization wrapper to iterator (#87459)
This is temporary fix for internal SEV. We have run three different workflows to validate this fix would unblock internal SEV.
And, those are a few following-up tasks:
- [ ] Create reproducible test for multithreading with generator
- [ ] Figure out how to make fullsynciterator is working properly with generator
- [ ] Move Wrapper back to generator if needed
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87459
Approved by: https://github.com/NivekT
