Unfriend Variable factory functions. (#28601)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28601
In the process, I moved AutogradMeta out of the Variable class. The
intent here is that I'm going to delete Variable class entirely,
so I had better not be putting stuff in it!
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Differential Revision: D18171160
Pulled By: ezyang
fbshipit-source-id: 9c0bcdc82797eca0577d1b0745b4a2ae962f3010
