[distributed] make the pickler in distributed_c10d pluggable (#53060)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53060
As title. We would like to use alternative pickler/unpickler
implementations, to make it possible to send objects over the wire that
are coming from a torch.package
Test Plan: Imported from OSS
Reviewed By: mrshenli
Differential Revision: D26737317
Pulled By: suo
fbshipit-source-id: 6bdef9824e48ef657dcad72cc5a9114e6612ea4a
