Add alias dispatch key Math. (#44354)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/44354
Test Plan: Imported from OSS
Reviewed By: ezyang
Differential Revision: D23591481
Pulled By: ailzhang
fbshipit-source-id: 6e93c4ec99a07f3fc920ba2d09dc222e6ced5adf
