[WIP] Add support for GIT in image-to-text and VQA pipelines

[st81]

What does this PR do?

Fixes #21110

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

Who can review?

@ArthurZucker @amyeroberts

[st81]

This PR is WIP. There are remaining tasks.

• Update GitTokenizer to contain required preprocessing
• Confirm GitTokenizerFast is importable
• Update tokenizer_config.json of GitForCausalLM

[amyeroberts]

Thanks for opening this PR! Let us know when it's ready for review 🤗

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

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