fixing image_utils.py todo

[skochar1]

What does this PR do?

This PR resolves a longstanding TODO in src/transformers/image_utils.py by replacing the use of logger.warning with Python’s built-in warnings.warn for notifying users of unused or invalid parameters in image processor functions. This approach makes warnings more controllable, user-friendly, and consistent with Python best practices.

Specifically, this PR:

• Fixes a TODO comment by swapping logging for proper warning handling using warnings.warn(..., UserWarning, stacklevel=2).
• Adds/updates docstrings and type hints for the affected functions.
• Implements comprehensive tests in tests/utils/test_image_utils.py to cover all usage scenarios—including valid parameters, invalid parameters, and edge cases.
• Ensures warning messages are triggered and formatted as expected.
• Verifies correctness through syntax, imports, and end-to-end integration checks.

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?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

@amyeroberts @qubvel

Failures

Failures unrelated to changes made by PR.

[qubvel]

cc @yonigozlan