[EP ABI] Add OpAttr_GetTensorAttributeAsOrtValue and replace the existing Node_GetTensorAttributeAsOrtValue (#25886)
### Description
Replace `Node_GetTensorAttributeAsOrtValue` with
`OpAttr_GetTensorAttributeAsOrtValue`.
Change the API signature to make it one of the `OpAttr` interfaces
instead of the `OrtNode` interface.
The original API was added
[here](https://github.com/microsoft/onnxruntime/pull/25566).