Migrate CPU cross and some elementwise to c10::complex (#38023)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/38023
Test Plan: Imported from OSS
Differential Revision: D21518304
Pulled By: anjali411
fbshipit-source-id: a7d7bad7ba0af66314a5e91608add32d36695e6b
