onnxruntime

Support direct usage of ORT format model flatbuffer for initializers (#12465)

* Add ability to use ORT format model flatbuffer directly for intiializers by leveraging the TensorProto external data infrastructure.

Requires user to provide ORT format model bytes when creating the session, and set both `session.use_ort_model_bytes_directly` and `session.use_ort_model_bytes_for_initializers` to 1 in SessionOptions config entries (AddSessionConfigEntry in C API).