add python API to print all operators that have kernels registered to a particular DispatchKey (#63575)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/63575
Test Plan: Imported from OSS
Reviewed By: ezyang, Chillee
Differential Revision: D30426919
Pulled By: bdhirsh
fbshipit-source-id: b0e487e48dfe02f7b9d678403f0a2b5bfe146f4e
