Deprecates calling linspace and logspace without setting steps explicitly (#43860)
Summary:
**BC-breaking note**
This change is BC-breaking for C++ callers of linspace and logspace if they were providing a steps argument that could not be converted to an optional.
**PR note**
This PR deprecates calling linspace and logspace wihout setting steps explicitly by:
- updating the documentation to warn that not setting steps is deprecated
- warning (once) when linspace and logspace are called without steps being specified
A test for this behavior is added to test_tensor_creation_ops. The warning only appears once per process, however, so the test would pass even if no warning were thrown. Ideally there would be a mechanism to force all warnings, include those from TORCH_WARN_ONCE, to trigger.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43860
Reviewed By: izdeby
Differential Revision: D23498980
Pulled By: mruberry
fbshipit-source-id: c48d7a58896714d184cb6ff2a48e964243fafc90
