Migrate CUDA cat, scatter, gather, index, index_put to c10::complex (#37650)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/37650
Test Plan: Imported from OSS
Differential Revision: D21394299
Pulled By: anjali411
fbshipit-source-id: dd7666af736e720b54b978cc62570d0e840e092f
