fix: inject processor into data handler fn_kwargs

[YashasviChaurasia]

Description of the change

DataPreProcessor.__execute_map_data_handler injected self.tokenizer into handler fn_kwargs but not self.processor. This caused
prepare_multimodal_data_processor to fail with ValueError: Processor is missing during vision model (e.g., LlavaNext/Granite Vision) fine-tuning, even
though the processor was correctly loaded and stored on the DataPreProcessor instance.

Related issue number

N/A — related slack thread: https://ibm-research.slack.com/archives/C0698T0FW3S/p1771832445118339

How to verify the PR

python -m pytest tests/data/test_data_preprocessing.py::test_multimodal_processor_injection_in_data_pipeline
tests/data/test_data_preprocessing.py::test_multimodal_processor_missing_raises_error -v

Was the PR tested

• I have added >=1 unit test(s) for every new method I have added.
• I have ensured all unit tests pass

[github-actions]

Thanks for making a pull request! 😃
One of the maintainers will review and advise on the next steps.

[dushyantbehl]

LGTM