Add docstrings to dspy/predict/refine.py and dspy/predict/best_of_n.py

[aviraldua93]

Claiming dspy/predict/refine.py and dspy/predict/best_of_n.py for docstring additions, as described in #8926.

Files:

• dspy/predict/refine.py — Adding docstrings to Refine.forward(), inspect_modules(), and recursive_mask()
• dspy/predict/best_of_n.py — Adding docstring to BestOfN.forward()

All docstrings follow the Google Python Style Guide with Args, Returns, and Raises sections.

PR incoming shortly.