chore(llmobs): add GEPA as alternative prompt optimization backend#16599

tillwf wants to merge 4 commits intomainDataDog/dd-trace-py:mainfrom

till.wohlfarth/MLOB-5317/prompt_optimization_gepaDataDog/dd-trace-py:till.wohlfarth/MLOB-5317/prompt_optimization_gepaCopy head branch name to clipboard