Allow modifications of attributes in modular

[molbap]

What does this PR do?

Often, attributes are not derived from model names. Modular files based on a given model are then bloated because there is a tiny change in an attribute, needing the entire thing to be rewritten. See https://github.com/huggingface/transformers/pull/41224/files here for instance.

This introduces an attribute renamer, from an arbitrary attribute name to another.

  class DINOv3ViTForImageClassification(Dinov2ForImageClassification):
      _attribute_renames = {"dinov2": "dinov3"}

On the attached PR, this expands the modeling file correctly.

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[molbap]

After internal discussion: this would harm the overall modular philosophy, adding a mutable inside classes like this. For the moment, we accept rewriting modular files which differ just by an attribute naming. (cc @yonigozlan )

Instead, a util to convert on load with 0 cost would be preferrable, and is in the works. cc @Cyrilvallez @ArthurZucker