Use `config.layer_norm_eps` in some `nn.LayerNorm`.
# What does this PR do?

⚠️⚠️⚠️ This changes the `eps` of those LayerNorm layers from (the default) `1e-5` to `1e-12`, and the outputs will have slightly differences before/after this PR. ⚠️⚠️⚠️

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Similar to #20554, but this time instead of removing the attribute from config, we use `config.layer_norm_eps` in some `nn.LayerNorm`.



_The documentation is not available anymore as the PR was closed or merged._<|||||>Just to confirm:

> - these changes don't have an impact on the integration tests, right? This only results in different outputs when one would train these models from scratch?

It has impact even for integration tests: the change is the **constant** `eps` being changed, which affects the forward call both in inference as well as in training.


- technically we should check the `layer_norm_eps` for each paper to match the original code

I agree - but I am not sure, for recent models, if all these attributes are set according to the papers, or people just used add new model like templates ...<|||||>This is too breaking I think. We need to be more careful on new models added that this attribute is consistently used but I don't think we should touch old models like this as it will change the results of the forward.<|||||>OK! I will keep this list of models to skip in the WIP PR where we add a test for checking unused config attributes.<|||||>Close as it is too breaking!