Add outer export to onnx (#53603) (#54869)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54869
Add symbolic fuction to support torch.outer export to onnx.
Support for transfo-xl-wt103 model.
Test Plan: Imported from OSS
Reviewed By: nikithamalgifb
Differential Revision: D27408978
Pulled By: SplitInfinity
fbshipit-source-id: 70c89a9fc1a5e4a4ddcf674afb1e82e492a7d3b9
