Split function schema parser from operator (#19280)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19280
We want to use the function schema parser from ATen/core, but with as little dependencies as possible.
This diff moves the function schema parser into its own file and removes some of its dependencies.
Reviewed By: dzhulgakov
Differential Revision: D14931651
fbshipit-source-id: c2d787202795ff034da8cba255b9f007e69b4aea
