Codegen: Generate static dispatch headers per operator (#68714)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68714
This splits the static dispatch headers (e.g. `CPUFunctions.h`)
into per operators headers (e.g. `ops/empty_cpu_dispatch.h`) which is
needed for when `Tensor.h` is compiled with static dispatch enabled.
There are also several places in ATen where the static dispatch
headers are used as an optimization even in dynamic dispatch builds.
Test Plan: Imported from OSS
Reviewed By: jbschlosser
Differential Revision: D32596265
Pulled By: albanD
fbshipit-source-id: 287783ef4e35c7601e9d2714ddbc8d4a5b1fb9e5
