FEAT Add JailBreakV-28K dataset

[apoorvdarshan]

Summary

• Adds the JailBreakV-28K dataset loader (_JailbreakVDataset) to pyrit.datasets
• Supports both JailBreakV_28K (28,300 jailbreak prompts) and RedTeam_2K (2,000 red team queries) configs
• Defaults to the mini_JailBreakV_28K split (280 rows) for lightweight usage
• Sets harm_categories from the dataset's policy column (16 safety policy categories)

Closes #1007

Test plan

• Unit tests for initialization defaults and custom configs/splits
• Unit tests for fetching with both JailBreakV_28K and RedTeam_2K configs
• Unit tests for skipping empty prompts, empty policy handling, and error on empty dataset
• Unit tests for optional metadata fields

References

• Paper: https://arxiv.org/abs/2404.03027
• Dataset: https://huggingface.co/datasets/JailbreakV-28K/JailBreakV-28k