onnxruntime

3b259e11 - [EP ABI] Utility to serialize OrtGraph to GraphProto (#25292)

[EP ABI] Utility to serialize OrtGraph to GraphProto (#25292) ### Description - Provides utility functions that serialize an `OrtGraph` to a `GraphProto` or `ModelProto`. - Header-only file that can be copied to a project that builds with ORT and ONNX. - Available in [include/onnxruntime/core/providers/utils/ort_graph_to_proto.h](https://github.com/microsoft/onnxruntime/blob/adrianl/ep-abi-ort-graph-to-onnx-protobuf/include/onnxruntime/core/providers/utils/ort_graph_to_proto.h) - Updates the `Node_GetSubgraphs` API function to also return the attribute names associated with each subgraph. This is required to determine which subgraph corresponds to a given attribute. - Adds `Graph_GetNumOperatorSets` and `Graph_GetOperatorSets` API functions to get the opset version for each domain. ### Motivation and Context Provide a utility to facilitate porting of existing execution providers to the new EP ABI. The utilities introduced by this PR convert an `OrtGraph` into an ONNX protobuf representation, which some existing EPs currently convert to their internal representation. Ideally, we would prefer a more direct conversion from a `OrtGraph` to the EP's internal representation, but this is a large effort. These utilities enable an incremental transition.