Make .circleci Conf class uses dataclasses; use types. (#21284)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21284
ghimport-source-id: a628af85b7a085e15903168e957bed1e273d6636
Differential Revision: D15621908
Pulled By: ezyang
fbshipit-source-id: 64e2da8b96cdc1b53c0b314771d225eebf3d4b2d
