[backport-aws-3.17] Sync CI configuration with main branch

[mrodm]

TL;DR

Syncs .buildkite and .github CI configuration from main to the
backport-aws-3.17 backport branch.

This brings automated backport workflows, new CI scripts, Go tooling, and
GitHub Actions that only work when they are present on the target branch itself.

Proposed commit message

Sync CI configuration with main branch for backport-aws-3.17.

Keep CI pipelines, GitHub Actions, and tooling consistent between active backport
branches and `main`, so that automated backport workflows and tooling improvements
land on all supported branches.

WHY:
GitHub Actions resolves workflow files from the branch where the event occurs,
not from `main`. Backport-branch workflows (changelog sync, post-backport
checklist, owner checks, auto-backport) must be present on the backport branch
itself to fire correctly.

Author's Checklist

• CI configuration files have been synced verbatim from main.

How to test this PR locally

N/A — this PR only syncs CI configuration files.

Related issues

• Relates backport: deploy backport-branch automation workflows to active backport branches #19262

---

This PR was generated with the assistance of Claude (claude-sonnet-4-6).

[infra-vault-gh-plugin-prod]

💔 Build Failed

• Buildkite Build
• Commit: 4702836

Failed CI Steps

• Check integrations activemq
• Check integrations aws
• Check integrations cyberarkpas
• Check integrations elastic_security
• Check integrations etcd
• Check integrations haproxy
• Check integrations jolokia
• Check integrations m365_defender
• Check integrations netskope
• Check integrations php_fpm
• Check integrations pps
• Check integrations sentinel_one_cloud_funnel
• Check integrations trendmicro
• Check integrations watchguard_firebox
• Check integrations zscaler_zia
• :junit: Junit annotate

History

cc @mrodm

[elastic-vault-github-plugin-prod]

🚀 Benchmarks report

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