Add support for builtins as attributes (#31269)
Summary:
Fixes #27495
This adds builtins as another piece of a concrete type. They're separate from normal functions since they represent the `BuiltinFunction` sugared value (which is a direct call to a builtin op). It also moves the builtins related logic from `jit/__init__.py` to `jit/_builtins.py` so it can be used from `jit/_recursive.py` to look up functions in the builtins table.
](https://our.intern.facebook.com/intern/diff/19149779/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31269
Pulled By: driazati
Differential Revision: D19149779
fbshipit-source-id: d4e5e5d7d7d528b75a2f503e6004394251a4e82d
