member, server: randomly check the etcd leader health to proactively resign

[JmPotato]

What problem does this PR solve?

Issue Number: ref #7499.

What is changed and how does it work?

Randomly check the etcd leader health to proactively resign.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

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[ti-chi-bot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[codecov]

Codecov Report

Merging #7661 (0bfaa4d) into master (754095a) will increase coverage by 0.01%.
Report is 11 commits behind head on master.
The diff coverage is 89.74%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7661      +/-   ##
==========================================
+ Coverage   73.87%   73.89%   +0.01%     
==========================================
  Files         429      429              
  Lines       47376    47415      +39     
==========================================
+ Hits        35000    35038      +38     
+ Misses       9392     9384       -8     
- Partials     2984     2993       +9     

Flag	Coverage Δ
unittests	73.89% <89.74%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[JmPotato]

/hold

[JmPotato]

/unhold

[JmPotato]

/hold