Fix Native signature for optional Tensor arguments (#50767)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50767
The native signature for optional tensor arguments wrongly produced "Tensor" instead of "optional<Tensor>". We didn't notice this because all internal ops currently use hacky_wrapper, and for hacky_wrapper, "Tensor" is correct.
This PR fixes that and ports one op (batch_norm) to not use hacky_wrapper anymore as a proof of fix.
ghstack-source-id: 120017543
Test Plan: waitforsandcastle
Reviewed By: bhosmer
Differential Revision: D25960941
fbshipit-source-id: ca6fe133109b5d85cff52390792cf552f12d9590
