ES|QL: Simplify CHUNK examples and enable CSV tests

[kderusso]

Simplifies docs example for ES|QL CHUNK function and allows CSV tests to run chunking tests.

[github-actions]

🔍 Preview links for changed docs

• docs/reference/query-languages/esql/kibana/docs/functions/chunk.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-search-relevance (Team:Search Relevance)

[elasticsearchmachine]

Pinging @elastic/core-docs (Team:Docs)

[ioanatia]

don't throw tomatoes at me, but this still could look better 🙈 - the way we render multi valued strings in the docs could be improved, because looking at the results, it's not super obvious we return multiple values:

ROW result = CHUNK("It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief.", {"strategy": "word", "max_chunk_size": 10, "overlap": 1})
| MV_EXPAND result

just a suggestion, feel free to also merge it as it is.