Fix duplicate arguments passed to dummy inputs in ONNX export
# What does this PR do?

This PR fixes: 

- a bug that was introduced in #15658 where a preprocessor and tokenizer were being passed together to the `generate_dummy_inputs()` function during the ONNX export.
- an oversight in the refactoring of the ONNX config for M2M-100

It also removes problematic TensorFlow integration tests, where the model implementation doesn't have parity with the PyTorch one (e.g. `camembert-base` is missing the causal LM head in TensorFlow). I'll address those issues in separate PRs as it involves touching the TensorFlow modeling files.

With these fixes, all slow ONNX tests now pass in all environments (only `torch`, only `tensorflow`, `torch` and `tensorflow`):

```bash
RUN_SLOW=1 python -m pytest tests/onnx/test_onnx_v2.py
```

cc @michaelbenayoun 
_The documentation is not available anymore as the PR was closed or merged._