Add support for boxed functors (#62658)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62658
Boxed functors, like their unboxed brethren, support operators which
aren't just a function pointer, but a function pointer with some
associated global state that is allocated at registration time.
The use case I have in mind with this implementation is "dispatcher
API from Python", where the extra state kernel registrations need is
the PyObject callable we will invoke to do the actual invocation.
See next PR in this stack.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Reviewed By: bhosmer
Differential Revision: D30074925
Pulled By: ezyang
fbshipit-source-id: ee040edbbec1e607486d338d1ea78bb5c6b2ece9
