OSPP-Week6: Debug CRR and implement new algorithm

[pilgrimygy]

@findmyway
last week's plan. In last week, I finish the PLAS algorithm, and it works well. But continuous CRR algorithm performance is poor.

Week 6:

1. Continue to fix continuous CRR bugs.
2. Implement new algorithms. The current plan includes UWAC and FisherBRC published on ICML'21.