pytorch

645a5f70 - move `flatten_dense_tensors` and `unflatten_dense_tensors` to Native (#58006)

move `flatten_dense_tensors` and `unflatten_dense_tensors` to Native (#58006) Summary: https://github.com/pytorch/pytorch/issues/55240 CC ngimel Pull Request resolved: https://github.com/pytorch/pytorch/pull/58006 Reviewed By: agolynski Differential Revision: D28386749 Pulled By: ngimel fbshipit-source-id: 4860c35d5ff95bcc38a243d7001180e7bd536314