[ONNX] Support large attribute and subgraph for large model (#38793)
Summary:
Previously large tensor data in attributes and subgraphs are not stored externally. ONNX won't be able to serialize the model for cases where the total size sums up to >= 2GB. This PR enables that.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38793
Reviewed By: hl475
Differential Revision: D22111092
Pulled By: houseroad
fbshipit-source-id: 355234e50825d576754de33c86a9690161caaeaf
