[numpy] `torch.angle`: promote integer inputs to float (#49163)
Summary:
**BC-Breaking Note:**
This PR updates PyTorch's angle operator to be consistent with NumPy's. Previously angle would return zero for all floating point values (including NaN). Now angle returns `pi` for negative floating point values, zero for non-negative floating point values, and propagates NaNs.
**PR Summary:**
Reference: https://github.com/pytorch/pytorch/issues/42515
TODO:
* [x] Add BC-Breaking Note (Prev all real numbers returned `0` (even `nan`)) -> Fixed to match the correct behavior of NumPy.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49163
Reviewed By: ngimel
Differential Revision: D25681758
Pulled By: mruberry
fbshipit-source-id: 54143fe6bccbae044427ff15d8daaed3596f9685
