Develop sys ut

[KomachiSion]

Please do not create a Pull Request without creating an issue first.

What is the purpose of the change

For #4981

Brief changelog

XX

Verifying this change

XXXX

Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a Github issue filed for the change (usually before you start working on it). Trivial changes like typos do not require a Github issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Format the pull request title like [ISSUE #123] Fix UnknownException when host config not exist. Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency exist. If the new feature or significant change is committed, please remember to add integration-test in test module.
• Run mvn -B clean package apache-rat:check findbugs:findbugs -Dmaven.test.skip=true to make sure basic checks pass. Run mvn clean install -DskipITs to make sure unit-test pass. Run mvn clean test-compile failsafe:integration-test to make sure integration-test pass.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.97%. Comparing base (ec34377) to head (4bb27cc).
Report is 3 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #12728      +/-   ##
=============================================
+ Coverage      69.62%   70.97%   +1.34%     
- Complexity      9417     9614     +197     
=============================================
  Files           1275     1275              
  Lines          41236    41260      +24     
  Branches        4374     4375       +1     
=============================================
+ Hits           28710    29283     +573     
+ Misses         10442     9888     -554     
- Partials        2084     2089       +5     

Files with missing lines	Coverage Δ
...c/main/java/com/alibaba/nacos/sys/env/EnvUtil.java	91.97% <ø> (+68.02%)	⬆️
...va/com/alibaba/nacos/sys/file/WatchFileCenter.java	81.57% <ø> (+81.57%)	⬆️
.../com/alibaba/nacos/sys/utils/ApplicationUtils.java	100.00% <100.00%> (+92.85%)	⬆️

... and 22 files with indirect coverage changes

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