extend serialization for tensor metadata (#99808)
Fixes #ISSUE_NUMBER
Add the serialization logic of backend metadata to the serialization of tensor, which is implemented through custom registration functions.
In #97429 , the structure backendMeta is provided in TensorImpl, and we think that this part of information may also need to be serialized for custom.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99808
Approved by: https://github.com/ezyang
