empty_cpu: Add functions that don't depend on Tensor (#70613)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70613
This refactors `at::detail::empty_cpu` to use only `TensorBase` so you
can construct tensors without including `Tensor.h`. It also adds a
`TensorOptions` version to reduce friction in operators moving from
the `at::empty` API.
Test Plan: Imported from OSS
Reviewed By: samdow
Differential Revision: D33623682
Pulled By: ngimel
fbshipit-source-id: 7a7b08bc2ed06830a3d698197a0c8389a096dc1d
(cherry picked from commit 2e17ad0bbd6dea2ea99c264fe3ea66414c991c8e)
