[Unified Search] Change phrase(s) comboboxes to async patterns

[cee-chen]

Summary

This PR does NOT address #158876, but helps reduce the confusion/cognitive dissonance of the async search results only matching on words from the start of the string, vs. EuiComboBox showing search results from anywhere in the string by default.

Please see https://eui.elastic.co/#/forms/combo-box#async for more documentation on async searching.

Before

After

Checklist

• [ ] Unit or functional tests were updated or added to match the most common scenarios No tests found
• 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)
• This renders correctly on smaller devices using a responsive layout. (You can test this in your browser)
• This was checked for cross-browser compatibility

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 3ab37e1

Metrics [docs]

Async chunks

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

id	before	after	diff
unifiedSearch	213.7KB	213.8KB	+96.0B

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

[mbondyra]

That's a good improvement! LGTM 👌🏼

[cee-chen]

Thank you Marta!