Bump golangci lint to v2

[ivanvc]

Required to bump to Go 1.25.1. Follow up on #19692/#19751/#19712.

Link to #20602.

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

[k8s-ci-robot]

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

[ivanvc]

/test pull-etcd-verify

[ivanvc]

/test pull-etcd-verify

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.11%. Comparing base (d46722b) to head (c2a53f7).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

see 21 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #20620      +/-   ##
==========================================
- Coverage   69.22%   69.11%   -0.12%     
==========================================
  Files         420      420              
  Lines       34780    34780              
==========================================
- Hits        24078    24038      -40     
- Misses       9309     9340      +31     
- Partials     1393     1402       +9     

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[ahrtr]

@ivanvc please rebase this PR, thx

[ivanvc]

/cc @ahrtr

[k8s-ci-robot]

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