Extend TensorImpl with BackendMeta (#97429)
BackendMeta offers a binary interface for the backend to attach arbitrary data to TensorImpl. TensorImpl has exactly one "slot" for backend metadata, however backend is free to compose any structure that is opaque to the framework beyond iheriting standard BackendMeta base.
Change-Id: I670fcdd16dd1c2b00f7eaa1cbc5b5dfea59a6221
Fixes #ISSUE_NUMBER
Pull Request resolved: https://github.com/pytorch/pytorch/pull/97429
Approved by: https://github.com/ezyang
