Expose an API to iterate all the registered operators (#23207)
Summary:
So we can iterate over the operator registry, and check the backward compatiblity.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23207
ghstack-source-id: 89570438
Test Plan: ci and the round trip tests added in the last diff
Reviewed By: zrphercule
Differential Revision: D16434335
fbshipit-source-id: 86a66d746a1f122a8aafe39e936606d6ba7ef362
