simplify op name determination into a single forward pass (#64261)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64261
Note that this does not preserve byte-for-byte compatibility with
existing names.
Test Plan:
* Rely on CI to catch gross errors.
* Merge after release cut to catch subtle issues.
Reviewed By: albanD
Differential Revision: D30700647
Pulled By: dagitses
fbshipit-source-id: 7b02f34b8fae3041240cc78fbc6bcae498c3acd4
