Refactor iterables (#29138)
Summary:
Refactor list comprehensions so they go through the same path as other for loops, making List Comprehensions work with modulelists, also fixing https://github.com/pytorch/pytorch/issues/27255
Replacing https://github.com/pytorch/pytorch/pull/28296 which was gh-poisoned and previously accepted.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29138
Differential Revision: D18303432
Pulled By: eellison
fbshipit-source-id: 8e4c0ba6f800142d5c4d921d56917cfae0c74655
