[R-282] use callbacks to trace reasoning of `Prompt`

[JinSeoung-Oh]

Hi, at first, I want to say thanks this wonderful work.

Actually, I want save the reason of evaluation. I mean, line 69 to line 106 at https://github.com/explodinggradients/ragas/blob/main/src/ragas/metrics/_answer_correctness.py Actually, it already has save function and it seems save line 69~106. Ah, of course it is example, but I think this module generate something like this line. I just want to save it

But I tried use this save function, it returned 'None'

So, how can I save this? I have to build new module for this?

Thanks!

_R-282