have stream generate ValidationOutcome

[zsimjee]

Problem

Streaming output originally looked like a string.

Raw LLM Output = xyz
Validated Output = xyz

This formatting is unusable for several reasons. It also doesn't support streaming into pydantic models.

Changes

1. Change the StreamRunner to return Generator[ValidationOutcome, None, None] instead of Generator[str, None, None]
2. Make sure that validation outcome is loaded with the parsed and validated run output, without doing a json.dumps
3. Split up run.py into 4 files for readability

Note: validation_passed is poorly calculated. We need to interop with validation better and expose why validation fails per unit.

[ShreyaR]

lgtm! left a small nit, feel free to merge once fixed