[DRAFT] [BREAKING] FEAT Refactor Harm Category as StrEnum

[eugeniavkim]

Description

In order to make harm_categories easier to search through and group by some alias names, this PR refactors our previous String harm categories into a class HarmCategory with categories that are not included in the list to be recognized in an OTHER category. This also does not include all harm categories, but others can continue to add harm areas that they would like to probe for and score with.

This PR is a breaking change as it does affect all datasets, SeedPrompt initialization, and tests.

The following items must be complete before changing from DRAFT Status:

• [ ] Refactor each dataset to map its harm categories to the new class HarmCategory
• [ ] Update DB queries