Lazy load `pandas` when importing pytorch (#71316)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/71313
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71316
Reviewed By: wenleix
Differential Revision: D33595043
Pulled By: malfet
fbshipit-source-id: da8c7a7f132696645191d7b7055c4c21970d92c3
(cherry picked from commit 2d4847780a4d26426d2300861069160836130063)
