[Draft] Add Eurobert configuration for ONNX export

[DWarez]

What does this PR do?

Adding configuration for Eurobert ONNX export support

Fixes # (2300)

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

Who can review?

@fxmarty, @echarlaix, @JingyaHuang, @michaelbenayoun

[DWarez]

I created a configuration to support Eurobert, but I'm still unsure about its correctness. When exporting the model, I'm getting some trace warnings:

/python3.11/site-packages/transformers/modeling_attn_mask_utils.py:122: TracerWarning: Converting a tensor to a Python boolean might cause the trace to be incorrect. We can't record the data flow of Python values, so this value will be treated as a constant in the future. This means that the trace might not generalize to other inputs!
  if (input_shape[-1] > 1 or self.sliding_window is not None) and self.is_causal:

python3.11/site-packages/transformers/modeling_attn_mask_utils.py:196: TracerWarning: torch.tensor results are registered as constants in the trace. You can safely ignore this warning if you use this function to create tensors out of constant variables that would be the same every time you call this function. In any other case, this might cause the trace to be incorrect.
  inverted_mask = torch.tensor(1.0, dtype=dtype) - expanded_mask

As you can see they come from some modelling methods in the transformers library (which are invoked by the modelling eurobert scripts).

I investigated a bit and to me it's quite clear why the warnings are getting triggered, but I'm unsure about their impacts on the usability and correctness of the exported model.

Any suggestion about how to test this would be appreciated, thanks.

[IlyasMoutawwakil]

Hi ! thanks for the contribution, please move it to optimum-onnx as we are moving the entire onnx/ort integrations there.