pytorch

5de5dd2d - First step of refactor lower passes (#74219)

First step of refactor lower passes (#74219) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/74219 X-link: https://github.com/pytorch/fx2trt/pull/18 This is beginning diff for refactor and clean up stuff in lowering process and pass management. Test Plan: unit test Reviewed By: yinghai Differential Revision: D34764123 fbshipit-source-id: 57fa930abefae56654219225167b52d7dd79e03a (cherry picked from commit 2ae868c83561c1a0dada4fab1b938f35d59ba3f8)