onnxruntime

Fix the issue that the new generated EP context model not able to find external data (#23537)

Fix the issue that the new generated EP context model not able to find external data

### Description
The new generated EP context model was not able to find the external data file because it lost track of the source model path which used to locate the external initializers.

Relate to issue: https://github.com/microsoft/onnxruntime/issues/23358