Modify ProcessorTesterMixin for better generalization
Author: yonigozlan
Pull request: yes

# What does this PR do?
Follows this https://github.com/huggingface/transformers/pull/32544#discussion_r1713841324. It will help avoid rewriting many tests for `ProcessorTest` classes that inherit from `ProcessorTesterMixin`.
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## Who can review?

@molbap @zucchini-nlp @amyeroberts 

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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_32637). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

Thanks for the reviews! I have made the requested modifications, and removed now unnecessary tests for grounding-dino. If you think these modifications look ok I'll merge!