[ONNX] Allow registration of custom symbolics for aten namespace (#66481) (#67810)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/67810
Test Plan: Imported from OSS
Reviewed By: msaroufim
Differential Revision: D32181303
Pulled By: malfet
fbshipit-source-id: af2a715dc554b958fa3f5a7a8ae96cb3f7d112bb
