Retrieval Metrics: Updating HitRate and MRR for Evaluation@K documents...

Retrieval Metrics: Updating HitRate and MRR for Evaluation@K documents retrieved. Also adding RR as a separate metric (#12997)

* Updating metrics: MRR renamed to RR, HitRate updated for multi-doc evaluation and new separate MRR implementation

* Updated MRR and HitRate with requested changes

* Iteration w/ class attribute implementation for the calculation option choice