Add complex support to broadcast_coalesced (#48686)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/47330
Add support for DataParallel complex tensors by handling them as `torch.view_as_real` for `broadcast_coalesced`, `scatter` and `gather`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48686
Reviewed By: osalpekar
Differential Revision: D25261533
Pulled By: sidneyfletcher
fbshipit-source-id: 3a25e05deee43e053f40d1068fc5c7867cfa9686
