Doc/describe usage of batch structure metrics in pipeline tuning

[andsel]

Release notes

[rn:skip]

What does this PR do?

Updates docs after #18770

Why is it important/What is the impact to the user?

N/A

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 (and/or docker env variables)
• [ ] I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• [ ]

How to test this PR locally

N/A

Related issues

• Closes Update documentation after final work with the exposure of histograms #18008
• Closes Update documentation describing the windowing metric values for batch metrics #18007

[github-actions]

🤖 GitHub comments

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[mergify]

This pull request does not have a backport label. Could you fix it @andsel? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• If no backport is necessary, please add the backport-skip label

[github-actions]

✅ Vale Linting Results

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[github-actions]

🔍 Preview links for changed docs

• docs/reference/tuning-logstash.md