generic overrideable convolution for backends (#23562)
Summary:
One possible solution based on our discussion yesterday: ezyang gchanan zdevito
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23562
Differential Revision: D16998161
Pulled By: ailzhang
fbshipit-source-id: 07fe3a335f43b4205a421b3521aeb5fa4dc80279
