Bump Go to v1.23.12

[mboersma]

/kind cleanup

What this PR does / why we need it:

Updates the Go toolchain to v1.23.12.

go1.23.12 (released 2025-08-06) includes security fixes to the database/sql and os/exec packages, as well as bug fixes to the runtime. See the Go 1.23.12 milestone on our issue tracker for details.

Which issue(s) this PR fixes:

N/A, but see #5789 for the previous bump.

Special notes for your reviewer:

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• cherry-pick candidate

Release note:

NONE

[mboersma]

/cherry-pick release-1.20

[k8s-infra-cherrypick-robot]

@mboersma: once the present PR merges, I will cherry-pick it on top of release-1.20 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.20

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 53.06%. Comparing base (1916969) to head (9c90270).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5803   +/-   ##
=======================================
  Coverage   53.06%   53.06%           
=======================================
  Files         279      279           
  Lines       29677    29677           
=======================================
  Hits        15749    15749           
  Misses      13112    13112           
  Partials      816      816           

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[jackfrancis]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 4dd18f4fe36efde1b957f374b5ebfea458d8d1ee

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis

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• OWNERS [jackfrancis]

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[k8s-infra-cherrypick-robot]

@mboersma: new pull request created: #5804

In response to this:

/cherry-pick release-1.20

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.