[Discover] Make _index and _id optional in EsHitRecord to support ES|QL records

[davismcphee]

Summary

This PR updates the EsHitRecord type to make _index and _id optional in order to avoid dangerously casting ES|QL records (which may not have _index or _id) to EsHitRecord.

Checklist

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• Flaky Test Runner was used on any tests changed
• Any UI touched in this PR is usable by keyboard only (learn more about keyboard accessibility)
• Any UI touched in this PR does not create any new axe failures (run axe in browser: FF, Chrome)
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This renders correctly on smaller devices using a responsive layout. (You can test this in your browser)
• This was checked for cross-browser compatibility

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[davismcphee]

/ci

[davismcphee]

/ci

[davismcphee]

/ci

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 1f22e67

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/discover-utils	84	86	+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	809.1KB	809.2KB	+52.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
unifiedDocViewer	11.5KB	11.5KB	+13.0B

Unknown metric groups

API count

id	before	after	diff
@kbn/discover-utils	112	114	+2

History

• 💚 Build #214811 succeeded 8a9ce23
• 💔 Build #214597 failed f83b5c6

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

cc @davismcphee

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[stratoula]

Thanx Davis!

[jughosta]

LGTM 👍