Definition infrastructure for instruction count ubenchmarks (#53296)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53296
Part 1 of the instruction count microbenchmarks. This PR is focused on benchmark definition machinery. (Though you can run `main.py` to see it in action.) A summary of the system is given in the README.
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D26907092
Pulled By: robieta
fbshipit-source-id: 0f61457b3ce89aa59a06bf1f0e7a74ccdbf17090
