Add typing info for data members of utils.data.sampler classes (#33679)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/33490
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33679
Differential Revision: D20063099
Pulled By: ngimel
fbshipit-source-id: 1bbf71a65408d117019ab38d7d095cfd337f5d1e
