Fix AutoImageProcessor.register and documentation in auto processing modules

[MilkClouds]

What does this PR do?

This PR fixes several issues in the auto processing modules:

1. Fixes AutoImageProcessor.register bug: Removes incorrect validation logic that was copied from tokenizers. The validation checked for slow_image_processor_class attribute consistency, but fast image processors don't have this attribute (unlike fast tokenizers), causing the register method to fail when registering custom image processors.

2. Fixes documentation errors: Corrects copy-paste errors in docstrings where "tokenizer" was incorrectly used instead of the appropriate processor type (feature extractor, image processor, video processor).

3. Fixes typos: Corrects "fine" → "find" in comments across multiple auto modules.

4. Improves AutoVideoProcessor trust handling: Adds proper upstream repository extraction from video_processor_auto_map when resolving trust_remote_code.

Changes by file:

• feature_extraction_auto.py: Fixed typo and corrected docstring to reference feature extractors instead of tokenizers
• image_processing_auto.py: Removed incorrect slow_image_processor_class validation and fixed import in docstring example
• processing_auto.py: Fixed typo in comment
• tokenization_auto.py: Fixed typo in comment
• video_processing_auto.py: Fixed docstring reference and added upstream repo handling for trust_remote_code

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline,
  Pull Request section?
• Was this discussed/approved via a Github issue or the forum? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

@ArthurZucker @Rocketknight1 (auto modules and processing)

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: auto

[MilkClouds]

For reviewer's information: this PR is ready for review!

[Rocketknight1]

This is definitely one for @zucchini-nlp, but you might need to wait until she's back!