[4/4][DataPipe] Remove iterator depletion in Zipper (#89974)
Fixes: https://github.com/pytorch/data/issues/865
I will add another PR in torchdata to validate this change would solve the infinite datapipe problem (I have tested locally). This is one of the most annoying stack of PRs cause by separation between TorchData and PyTorch.
There is a case that `file.close` is never called because when generator function has never reached to the end. A simple example would be `zip` two datepipes with different length. The longer DataPipe would never reach the end of generator and then it will be cleaned up by `gc`. So, the line of `file.close` is not executed. (This is the reason that Vitaly has to create this [hack](https://github.com/pytorch/pytorch/blob/4451eb24e6287dff62ff8a7ec0eda6a6998807b0/torch/utils/data/datapipes/iter/combining.py#L573-L583) to retrieve all remaining data to make sure generator function is fully executed)
However, this hack introduces another problem where an infinite datapipe would make `zip` never end as it would try to deplete the infinite iterator. See: https://github.com/pytorch/data/issues/865
So, in this PR, I am adding a `try-finally` clause to make sure the `file.close` is always executed during the destruction of `generator` object. Then, we don't need the hack within `zip` any more.
Differential Revision: [D41699469](https://our.internmc.facebook.com/intern/diff/D41699469)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89974
Approved by: https://github.com/NivekT, https://github.com/wenleix
