Back out "Revert D19987020: [pytorch][PR] Add the sls tensor train op" (#43938)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43938
resubmit
Test Plan: unit test included
Reviewed By: mruberry
Differential Revision: D23443493
fbshipit-source-id: 7b68f8f7d1be58bee2154e9a498b5b6a09d11670
