Allow custom registration of shape functions (#73270)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73270
Together with open registration of NNC lowerings this should make possible to add support for custom operators, including internal fb-ops
Test Plan: Imported from OSS
Reviewed By: mrshenli
Differential Revision: D34451275
Pulled By: eellison
fbshipit-source-id: ae8ae2deb93caa6770e738217461e65853897b55
(cherry picked from commit ea6b7e8a6d8f970a20e68d02eefc5c951e32aa07)
