Models docstring
# What does this PR do?

This PR cleans up all docstrings following up from #20757 and #21199. It removes the need for the `processor_class` in TensorFlow and Flax generic examples by setting in the examples like #20757 did for PyTorch then makes a full pass across all models to clean up the docstrings (removing the processor_class` in the `add_code_sample` decorator, remove random outputs, use the auto classes for preprocessing).

Note that in some cases we can't use the auto-classes for preprocessing: when linking to the `__call__` method of a processor or image processor, we need the actual class (cc @amyeroberts I changed a couple of things you did here).
_The documentation is not available anymore as the PR was closed or merged._<|||||>Thank you @sgugger for cleaning this up. With all ~250 files, I will trust you instead of look lines by lines, except one question below.

I would definitely prefer to run a doctest first offline before merging this PR - for which I can launch on my side. From previous PRs, it has shown there are always some surprise. I will launch doctest CI when all reviewers give their approval.

**So here my question**

> Note that in some cases we can't use the auto-classes for preprocessing: when linking to the __call__ method of a processor or image processor, we need the actual class (cc @amyeroberts I changed a couple of things you did here).

I see even in such places, we still have
```python
Pixel values can be obtained using [`AutoImageProcessor`].  See [`ConvNextImageProcessor.__call__`] for details.
```
I don't have much context and prior knowledge, but is it true we want to use `AutoImageProcessor` but `ConvNextImageProcessor.__call__` in such cases?<|||||>> With all ~250 files, I will trust you instead of look lines by lines.

A review would still be much appreciated, as it could catch accidental typos.

> I would definitely prefer to run a doctest first offline before merging this PR - for which I can launch on my side. From previous PRs, it has shown there are always some surprise. I will launch doctest CI when all reviewers give their approval.

Sure, we can wait for that as long as the results are available before the release branch is cut.

> I don't have much context and prior knowledge, but is it true we want to use AutoImageProcessor but ConvNextImageProcessor.__call__ in such cases?

Yes.<|||||>I triggered the doctest CI against the (last) commit (so far) in this PR. Will take a look on the PR changes too :-)

[run page](https://github.com/huggingface/transformers/actions/runs/3987623228/jobs/6837694181)