feat: drand: refactor round verification

[simlecode]

关联的Issues (Related Issues)

https://github.com/filecoin-project/lotus/pull/11598/files

改动 (Proposed Changes)

附注 (Additional Info)

自查清单 (Checklist)

在你认为本 PR 满足被审阅的标准之前，需要确保 / Before you mark the PR ready for review, please make sure that:

• 符合Venus项目管理规范中关于PR的相关标准 / The PR follows the PR standards set out in the Venus project management guidelines
• 具有清晰明确的commit message / All commits have a clear commit message.
• 包含相关的的测试用例或者不需要新增测试用例 / This PR has tests for new functionality or change in behaviour or not need to add new tests.
• 存在兼容性问题（接口, 配置，数据，灰度），如果存在需要进行文档说明 / This PR has compatibility issues (API, Configuration, Data, GrayRelease), if so, need to be documented.
• 包含相关的的指南以及文档或者不需要新增文档 / This PR has updated usage guidelines and documentation or not need
• 通过必要的检查项 / All checks are green

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (cfc4cab) 25% compared to head (abf13fb) 25%.

Additional details and impacted files

@@            Coverage Diff            @@
##           feat/nv22   #6270   +/-   ##
=========================================
  Coverage         25%     25%           
=========================================
  Files            646     646           
  Lines          79847   79846    -1     
=========================================
+ Hits           20503   20504    +1     
+ Misses         56660   56657    -3     
- Partials        2684    2685    +1