refrator: 重构了discovery包，删除了重复的代码

[hunjixin]

关联的Issues (Related Issues)

close #5076

改动 (Proposed Changes)

1. 合并discovery和network包
2. 删除discovery中没用的代码，仅保留hello协议部分
3. 调整了启动顺序，修复了5076的bug

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.
• 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

Merging #5157 (e3073c1) into master (14d26a4) will decrease coverage by 0%.
The diff coverage is 61%.

❗ Current head e3073c1 differs from pull request most recent head c08b4c7. Consider uploading reports for the commit c08b4c7 to get more accurate results

@@           Coverage Diff           @@
##           master   #5157    +/-   ##
=======================================
- Coverage      25%     24%    -1%     
=======================================
  Files         597     592     -5     
  Lines       65586   65338   -248     
=======================================
- Hits        16554   16306   -248     
- Misses      46872   46886    +14     
+ Partials     2160    2146    -14     

[simlecode]

+LGTM

[diwufeiwen]

LGTM