Improve complex support in common_nn test machinery (#50593)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50593
There are no equivalent to torch.FloatTensor, torch.cuda.FloatTensor for complex
types. So `get_gpu_type` and `get_cpu_type` are broken for complex tensors.
Also found a few places that explicitly cast inputs to floating point types,
which would drop the imaginary component before running the test.
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D25954050
Pulled By: mruberry
fbshipit-source-id: 1fa8e5af233aa095c839d5e2f860564baaf92aef
