[warnings][Caffe2] Suppress warnings in caffe2 headers (#71196)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71196
`caffe2` headers contain code that can elicit warnings when built with strict compiler flags. Rather than force downstream/consuming code to weaken their compiler flags, suppress those warnings in the header using `#pragma clang diagnostic` suppressions.
Test Plan: CI Pass
Reviewed By: malfet
Differential Revision: D33536233
fbshipit-source-id: 74404e7a5edaf244f79f7a0addd991a84442a31f
