Time-series docs changes

[kkrik-es]

• Mark time series aggs as preview
• Expand rate description
• Fix preview tags for functions
• Add note in stats for time series aggs

[github-actions]

🔍 Preview links for changed docs

• docs/reference/query-languages/esql/kibana/docs/functions/rate.md

[github-actions]

ℹ️ Important: Docs version tagging

👋 Thanks for updating the docs! Just a friendly reminder that our docs are now cumulative. This means all 9.x versions are documented on the same page and published off of the main branch, instead of creating separate pages for each minor version.

We use applies_to tags to mark version-specific features and changes.

Expand for a quick overview

When to use applies_to tags:

✅ At the page level to indicate which products/deployments the content applies to (mandatory)
✅ When features change state (e.g. preview, ga) in a specific version
✅ When availability differs across deployments and environments

What NOT to do:

❌ Don't remove or replace information that applies to an older version
❌ Don't add new information that applies to a specific version without an applies_to tag
❌ Don't forget that applies_to tags can be used at the page, section, and inline level

🤔 Need help?

• Check out the cumulative docs guidelines
• Reach out in the #docs Slack channel

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)

[leemthompo]

Thanks for the follow up @kkrik-es! Couple of nits and I noticed one important thing (using the preview = true boolean)

[felixbarny]

Suggested change

	+ "Rate calculations account for changes in monotonicity, such as counter resets when a service restarts, and extrapolate "
	+ "Rate calculations account for counter resets such as when a service restarts, and extrapolate "

Monotonicity has a specific meaning in the context of OTel. The rate function still only applies to monotonic counters. Non-monotonic counters aka up-down-counters are used, for example, to measure the number of currently active requests. The phrase "changes in monotonicity" may therefore be misunderstood as it's not about a metric changing from being monotonic to non-monotonic.

If you want to mention the term monotonicity, maybe rephrase as "breaks in monotonicity", rather than "changes in monotonicity".

[kkrik-es]

Good call, changes to breaks in monotonicity that's inline with promql too.

[leemthompo]

Thanks again @kkrik-es 👍

[yannis-roussos]

LGTM, thanks for adding the more extended rate description @kkrik-es!