Make Python op registration work with torchdeploy/multipy (#87162)
See strategy at PythonOpRegistrationTrampoline.cpp for the
big picture.
Along the way, I made OperatorHandle support == and hashing,
and slightly changed the low level python_dispatch impl API
to disallow empty strings for dispatch key, which had the knock
on effect of requiring us to explicitly make sure we pass in
CompositeImplicitAutograd if we would have passed in "" (I didn't apply
this to the rest of the file because I'm lazy.)
Test strategy is we delete the logic for preventing Python op
registrations in torch from being skipped in a torchdeploy context
and show CI still works.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87162
Approved by: https://github.com/anjali411, https://github.com/bdhirsh
