Reland "add an API for external backends to register custom device names (#86992)" (#87453)
Re-land of https://github.com/pytorch/pytorch/pull/86992
This reverts commit a895af92506f206889610251624590798d0deabd.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87453
Approved by: https://github.com/ezyang, https://github.com/albanD
