Map model_type and doc pages names
# What does this PR do?

As discussed on [moon-landing](https://github.com/huggingface/moon-landing/pull/1692#discussion_r774957604), it's not possible to automatically generate the link to the documentation from the configuration of a model, due to multiple inconsistencies between model type and doc page name.

This PR fixes that and adds a script to make sure we have a model type for every documented model (for instance currently we have a mising model type for models having a tokenizer only, like Wav2Vec2-Phoeneme and they don't appear on the AutoTokenizer doc as a result) and that the doc page name matches the model type.

It breaks some links to the doc, but we (I and Julien) think this is acceptable.
very neat!<|||||>Sounds good to me. Will resolve conflicts and merge.