Propagate library_name parameter in from_pretrained to export (#2328)
* Propagate library_name parameter in from_pretrained to export
Required to avoid automatic inferring of the library_name
* Use class attribute for ORTModel instead
Under modeling_diffusion it looks like ORTModel isn't used
* Add test case
* Update optimum/onnxruntime/modeling_ort.py
---------
Co-authored-by: Ella Charlaix <80481427+echarlaix@users.noreply.github.com>