Add new defense algo and sampler

[xieyxclack]

The modifications included in this pr:

• Add a new sampler ResponsivenessRealtedSampler
• Add defense algo Krum:
  • To test the effectiveness of Krum, I add a gaussian attacker and change the expected types of cfg.attack.attacker_id from int to int/list, please double check this @Osier-Yi
  • And to fix the issue caused by merging int and list configuration items, I add a forced replacement rule to yacs, please double check this @yxdyc

BTM, these features have been developed and pushed into the branch submit_dev_branch before. This pr focuses on how to add a unit test for ensuring their effectiveness and promotes further development.

[yxdyc]

LGTM