migrate experimental-peer-skip-client-san-verification flag to feature gate

[wodeyoulai]

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

issue #19062

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: wodeyoulai
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[k8s-ci-robot]

Hi @wodeyoulai. Thanks for your PR.

I'm waiting for a etcd-io member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[siyuanfoundation]

I don't think this PR is correct.
Can you find the original PR that added this flag and change the owner to that author? Thanks!

[wodeyoulai]

Sorry.I've found the original author. I will update the PR with the correct owner shortly.

[siyuanfoundation]

/ok-to-test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.75%. Comparing base (5d47d7f) to head (2da0636).
Report is 9 commits behind head on main.

Additional details and impacted files

Files with missing lines	Coverage Δ
server/embed/etcd.go	75.90% <100.00%> (+0.04%)	⬆️
server/etcdmain/config.go	71.79% <ø> (ø)
server/features/etcd_features.go	60.00% <ø> (ø)

... and 19 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #19225      +/-   ##
==========================================
- Coverage   68.76%   68.75%   -0.02%     
==========================================
  Files         420      420              
  Lines       35650    35651       +1     
==========================================
- Hits        24514    24511       -3     
  Misses       9714     9714              
- Partials     1422     1426       +4     

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