Add temporary torch::k{name} enum declarations (#27051)
Summary:
This PR adds temporary declarations for `torch::k{name}` enums, so that we can submit a PR to rename the enum usage in torchvision. And then, after the changes to torchvision is done, we can remove the temporary declarations in https://github.com/pytorch/pytorch/pull/26837 to officially move over to using `c10::variant` for enums.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27051
Differential Revision: D17672220
Pulled By: yf225
fbshipit-source-id: 4ae77634e8c7efa3404698f7c1a69177cbb5dab3
