Fix failing release tests (Require capability for DECAY function and SET and INLINESTATS commands)

[craigtaverner]

Three PRs have just been merged that cause failures in test-release, and a third PR changes ES|QL railroad diagrams for another recently released change to KNN (also a snapshot-only feature).

• [ES|QL] Add Decay function #132729 - DecayTests has over 300 failures
• ES|QL: Add grammar for SET instruction #134029 - ParsingTests had six new failures
• ESQL: Ensure we fail nicely for invalid INLINESTATS queries #124725 - Failures in VerifierTests and OptimizerVerificationTests

This PR attempts to fix all in one, because if we do this in separate PRs they will fail due to the failures cause by the other PRs.

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)

[carlosdelest]

Thanks for fixing @craigtaverner !

[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-analytical-engine (Team:Analytics)

[luigidellaquila]

If the CI is happy, I'm happy as well.

Thanks @craigtaverner!

[timgrein]

Thank you for the fix!

[bpintea]

Thanks, Craig!