[ES|QL] Add a helper to retrieve the metadata columns

[stratoula]

Summary

Create a helper to retrieve the metadata columns (will come in handy for one discover project)

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

Pinging @elastic/kibana-esql (Team:ESQL)

[stratoula]

/ci

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 6d584f5

Failed CI Steps

• FTR Configs #83

Test Failures

• [job] [logs] FTR Configs #83 / InfraOps App Metrics UI Hosts View #With data #Single Host Flyout Tabs Overview Tab cpuUsage tile should show 48.3%

Metrics [docs]

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
@kbn/esql-utils	62	64	+2

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
discover	771.2KB	771.2KB	+2.0B

Unknown metric groups

API count

id	before	after	diff
@kbn/esql-utils	66	68	+2

History

• 💔 Build #231065 failed 63cbd7e

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[davismcphee]

Thanks @stratoula!