changelog: add note from CVE-2025-22869

[ivanvc]

Adds entries regarding the golang.org/x/crypto upgrade to 0.35.0, to address CVE-2025-22869.

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.88%. Comparing base (8e44d3a) to head (48fcef5).
Report is 9 commits behind head on main.

Additional details and impacted files

see 26 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #19479      +/-   ##
==========================================
+ Coverage   68.87%   68.88%   +0.01%     
==========================================
  Files         420      420              
  Lines       35779    35762      -17     
==========================================
- Hits        24642    24634       -8     
+ Misses       9711     9700      -11     
- Partials     1426     1428       +2     

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[ivanvc]

Note: I need @fuweid's changes in the v3.6 CHANGELOG from #19474. I rebased his branch to avoid conflicts, but because other commits were already in the main, it brought more commits. While removing them, it made me co-author Fu's commit.

I think the best would be if I manually rebase my branch once his pull request is merged.

[ahrtr]

Please rebase this PR, thx

[ivanvc]

/cc @ahrtr

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