Explicitly define supported types (#19516)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19516
Explicitly define types that are supported in kernel inputs and outputs.
Also, this allows us to show much nicer error messages if a user writes kernels with wrong argument types.
Reviewed By: ezyang
Differential Revision: D15020306
fbshipit-source-id: 55ebec81e075e874777acd59aa29a5578fc19ef7
