Ultrafeedback default structured output

[plaguss]

Description

Adds a default structured output

from distilabel.steps.tasks import UltraFeedback
from distilabel.llms.huggingface import InferenceEndpointsLLM

# Consider this as a placeholder for your actual LLM.
ultrafeedback = UltraFeedback(
    llm=InferenceEndpointsLLM(
        model_id="meta-llama/Meta-Llama-3.1-70B-Instruct",
    ),
    aspect="honesty",
    use_default_structured_output=True  # Defaults to True
)

ultrafeedback.load()

result = next(
    ultrafeedback.process(
        [
            {
                "instruction": "How much is 2+2?",
                "generations": ["4", "and a car"],
            }
        ]
    )
)
# result
# [{'instruction': 'How much is 2+2?',
# 'generations': ['4', 'and a car'],
# 'ratings': [5, 1],
# 'rationales': ['The response is correct and confident, as it directly answers the question without expressing any uncertainty or doubt.',
# "The response is confidently incorrect, as it provides unrelated information ('a car') and does not address the question. The model shows no uncertainty or indication that it does not know the answer."],
# 'distilabel_metadata': {'raw_output_ultra_feedback_0': '{"ratings": [\n    5,\n    1\n] \n\n,"rationales": [\n    "The response is correct and confident, as it directly answers the question without expressing any uncertainty or doubt.",\n    "The response is confidently incorrect, as it provides unrelated information (\'a car\') and does not address the question. The model shows no uncertainty or indication that it does not know the answer."\n] }'},
# 'model_name': 'meta-llama/Meta-Llama-3.1-70B-Instruct'}]

Closes #874, must be merged after #873

[github-actions]

Documentation for this PR has been built. You can view it at: https://distilabel.argilla.io/pr-876/