Add complex tensor dtypes for the __cuda_array_interface__ spec (#42918)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/42860
The `__cuda_array_interface__` tensor specification is missing the appropriate datatypes for the newly merged complex64 and complex128 tensors. This PR addresses this issue by casting:
* `torch.complex64` to 'c8'
* `torch.complex128` to 'c16'
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42918
Reviewed By: izdeby
Differential Revision: D23130219
Pulled By: anjali411
fbshipit-source-id: 5f8ee8446a71cad2f28811afdeae3a263a31ad11
