Add BetterTransformer support for RemBERT

[hchings]

What does this PR do?

Add BetterTransformer support for RemBERT (part of #20372)

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?

Details

• RemBERT's primary change is decoupling in/output embeddings. Since RemBERT uses the same Attention mechanism in BERT, it can use the same BertLayerBetterTransformer. (please correct me if I'm wrong)
• Minor code cleanup to sort model names alphabetically as the convention in transformers repo.
• All tests for encoders passed on GPU

cc @younesbelkada, @michaelbenayoun, @fxmarty. Thanks.

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[younesbelkada]

Thanks so much for adding BetterTransformer support for RemBERT 🎉
Very clean PR! Thanks also for taking care of the alphabetical order on the testing suite
Looking forward to your next contributions 💪

[hchings]

Hi @younesbelkada or @michaelbenayoun, I see that "first-time contributor needs a maintainer to approve running workflows". Could you help to approve that? Thanks!

[younesbelkada]

Thanks for the heads-up! Just run the workflow and we'll merge once it's green

[hchings]

Hi @younesbelkada, there are two checks failed.

1/ test_inference_speed() in test_bettertransformer_encoded.py: this test only runs on bert-base-uncased model and will pass on GPU (test screenshot attached above) but can occasionally fail on CPU. All BetterTransformer-related PRs could easily have this check failed. Should we open an Issue to look into this?

 AssertionError: 0.05959849110001869 not less than 0.056976150400032566 : The converted model is slower than the original model.

I think it's either PyTorch's issue or sth has to be changed in BertLayerBetterTransformer because even on CPU BetterTransformer is supposed to be faster. Please advise, thanks.

2/ ONNX Runtime - I saw this test has been failing on main branch. Since this is completely irrelevant to the code changes in this PR, can we ignore it for merging this PR?

[younesbelkada]

Hi @hchings
Thanks for your message
For 2/ this is expected as some tests are flaky so don't worry about that
For 1/ this is a bit strange since it passes on mac-os and not on ubuntu. This test used to be flaky and fails sometime. Let me get back to you on this

[younesbelkada]

Ok the test was just flaky, let's merge!