Add Windows 2025 for unit test steps (backport #42998)

[mergify]

Proposed commit message

Based on Support Matrix Windows 2025 should be included in 8.17 for filebeat and metricbeat only. Other active branches do not have Windows 2025 support.
Updated Extended Windows unit test group with additional step per beats mentioned above.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

• Relates: Beats Windows 2025 image #43077

Logs

Buildkite builds:
-- filebeat: https://buildkite.com/elastic/filebeat/builds/14161#0195618f-0cb5-4817-aaea-b40d90e895d2
-- metricbeat: https://buildkite.com/elastic/beats-metricbeat/builds/14661#0195618f-0de9-467b-ae6e-ec7ffc2f3ee8

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This is an automatic backport of pull request #42998 done by [Mergify](https://mergify.com).

[v1v]

LGTM. However, can you remove the reference for the GH private issue? Maybe you can transfer the private GH issue to this repository or create a new one and link to it. Whatever you prefer