test: update robustness doc and new case to reproduce 19179

[fuweid]

NOTE: It's still hard to reproduce it. It may take 5 minutes or few hours.

Closes: #19304

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

cc @ahrtr @serathius @siyuanfoundation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.88%. Comparing base (f1d09c0) to head (8866fce).
Report is 4 commits behind head on main.

Additional details and impacted files

see 20 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #19353      +/-   ##
==========================================
+ Coverage   68.83%   68.88%   +0.04%     
==========================================
  Files         420      420              
  Lines       35716    35716              
==========================================
+ Hits        24586    24602      +16     
+ Misses       9710     9694      -16     
  Partials     1420     1420              

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[fuweid]

/retest

[siyuanfoundation]

/lgtm

Thanks @fuweid !

[k8s-ci-robot]

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