Dump operator names of a module and its submodules.
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/29374
Test Plan: Imported from OSS
Reviewed By: ljk53
Differential Revision: D18372073
Pulled By: ljk53
fbshipit-source-id: cf2df0d44ffe74dd24dc63f1f07f395e36b5393d
