Increase pipeline support for ONNX export.
 Supports all kind of models for all the pipelines we've except `summarization` because of `triu`not supported by ONNX.
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/5005?src=pr&el=h1) Report
> Merging [#5005](https://codecov.io/gh/huggingface/transformers/pull/5005?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/9931f817b75ecb2c8bb08b6e9d4cbec4b0933935&el=desc) will **increase** coverage by `0.37%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/5005/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/5005?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #5005      +/-   ##
==========================================
+ Coverage   76.89%   77.26%   +0.37%     
==========================================
  Files         128      128              
  Lines       21854    21854              
==========================================
+ Hits        16804    16886      +82     
+ Misses       5050     4968      -82     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/5005?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/file\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/5005/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9maWxlX3V0aWxzLnB5) | `73.79% <0.00%> (+0.40%)` | :arrow_up: |
| [src/transformers/modeling\_tf\_xlm.py](https://codecov.io/gh/huggingface/transformers/pull/5005/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl94bG0ucHk=) | `75.85% <0.00%> (+19.75%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/huggingface/transformers/pull/5005?src=pr&el=continue).
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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/5005?src=pr&el=footer). Last update [9931f81...9f4da89](https://codecov.io/gh/huggingface/transformers/pull/5005?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
