Add Luke to Onnx
# What does this PR do?
I added lines to make Luke models available for Onnx conversion.

## Who can review?

- albert, bert, xlm: @LysandreJik

adding @NielsRogge since he worked on luke
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_16562). All of your documentation changes will be reflected on that endpoint.<|||||>
> ```
> RUN_SLOW=1 pytest tests/onnx/test_onnx_v2.py -k "luke"
> ```

I have all requirements installed and yet, I get the following output when I run the slow test:
```
RUN_SLOW=1 pytest tests/onnx/test_onnx_v2.py -k "luke"
================= test session starts==============================
platform darwin -- Python 3.9.12, pytest-7.1.1, pluggy-1.0.0
rootdir: /Users/aakash/work/transformers, configfile: setup.cfg
collected 141 items / 141 deselected / 0 selected                                                                                                                                                                                             
```
What am I missing?

<|||||>You need to add the luke architecture to be tested in `tests/onnx/test_onnx_v2.py`. 
Currently you are running those tests and filtering for the ones containing "luke" in their names, but none is found.<|||||>the slow tests resulted in the following errors:
[luke_onnx_test.log](https://github.com/huggingface/transformers/files/8608221/luke_onnx_test.log)
<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.<|||||>@lewtun could you revive this PR? Seems like it was already in a good state.<|||||>Hey @aakashb95 sorry for the slow reply! 

The reason your tests are failing is because:

* LUKE can't be loaded with `AutoModelForMaskedLM`. To solve this, please rebase your branch on `main` to include the recent changes in https://github.com/huggingface/transformers/pull/17499
* You need to import the `LukeForXxx` PyTorch classes in `features.py` [here](https://github.com/huggingface/transformers/pull/16562/files#diff-f4bad33d844c5d91b09dd0af27395ade640e907920b357daf125dd19458bdd60L38)
* You need to specify the outputs for the new features in `config.py` in the `_tasks_to_common_outputs` dictionary, e.g. add this:

```python
  "entity-classification": OrderedDict({"logits": {0: "batch"}}),
  "entity-pair-classification": OrderedDict({"logits": {0: "batch"}}),
  "entity-span-classification": OrderedDict({"logits": {0: "batch"}}),
```

After that, I think this PR should be in a good shape and the tests will pass :)<|||||>Thanks for reviving this PR!
I have incorporated the changes you mentioned and run the slow tests.

The tests fail with errors similar to the one below:
```log
self = <tests.onnx.test_onnx_v2.OnnxExportTestCaseV2 testMethod=test_pytorch_export_071_luke_entity_pair_classification>, test_name = 'luke_entity-pair-classification'
name = 'luke', model_name = 'studio-ousia/luke-base', feature = 'entity-pair-classification'
onnx_config_class_constructor = functools.partial(<bound method OnnxConfig.from_model_config of <class 'transformers.models.luke.configuration_luke.LukeOnnxConfig'>>, task='entity-pair-classification')
device = 'cpu'

    def _onnx_export(self, test_name, name, model_name, feature, onnx_config_class_constructor, device="cpu"):
        from transformers.onnx import export
    
        model_class = FeaturesManager.get_model_class_for_feature(feature)
        config = AutoConfig.from_pretrained(model_name)
>       model = model_class.from_config(config)
E       AttributeError: type object 'LukeForEntityPairClassification' has no attribute 'from_config'

tests/onnx/test_onnx_v2.py:266: AttributeError
```

If my understanding is correct, the `AutoModelFor*` classes have `from_config` implemented and since `luke` is unique, a `from_config` would have to be implemented for corresponding `LukeFor*` classes, right?

Attaching logs for reference:
[luke_onnx_slow_test.log](https://github.com/huggingface/transformers/files/8884467/slow_test.log)
 <|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.<|||||>cc'ing @lewtun here<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.