make python udf serialization format to be binary plus tensor tables (#27136)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27136
make python udf serialization format to be binary plus tensor tables, so that tensors can be attached to autograd graph, handled in the same way as builtin operators
ghstack-source-id: 91156141
Test Plan: unit tests
Reviewed By: pritamdamania87
Differential Revision: D17405686
fbshipit-source-id: 4a8c9804f6ad239eb0655fa5daeb54580d4741fd
