[Console] Update autocomplete route configuration to include proxy headers

[mibragimov]

Summary

This PR updates the autocomplete route configuration to include missing proxy headers such as x-forwarded-for,
x-forwarded-host, x-forwarded-port, and x-forwarded-proto to ensure that remote headers are forwarded to the Elasticsearch server. And also adds a check to ensure that the host header is set to the hostname if it is not already set. Users reported that the autocomplete indices were not showing up in the autocomplete dropdown in some cases due to the misconfiguration in autocomplete route. This PR should fix that issue.

This PR is only aimed to 8.6.x since in main we recently merged a PR which refactors this raw queries in favour of using the native es client which already takes into consideration proxy header and es ssl configurations.

Testing

To test this PR, verify that the correct headers are being sent to the Elasticsearch server when using the autocomplete route. You can use the console.log statement in the getEntity function to verify that the headers are being sent correctly.

Release note

This PR fixes an issue where the autocomplete indices were not showing up in the autocomplete dropdown in some cases due to the misconfiguration in autocomplete route.

Checklist

Delete any items that are not applicable to this PR.

• 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
• 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

Risk Matrix

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Before closing this PR, invite QA, stakeholders, and other developers to identify risks that should be tested prior to the change/feature release.

When forming the risk matrix, consider some of the following examples and how they may potentially impact the change:

Risk	Probability	Severity	Mitigation/Notes
Multiple Spaces—unexpected behavior in non-default Kibana Space.	Low	High	Integration tests will verify that all features are still supported in non-default Kibana Space and when user switches between spaces.
Multiple nodes—Elasticsearch polling might have race conditions when multiple Kibana nodes are polling for the same tasks.	High	Low	Tasks are idempotent, so executing them multiple times will not result in logical error, but will degrade performance. To test for this case we add plenty of unit tests around this logic and document manual testing procedure.
Code should gracefully handle cases when feature X or plugin Y are disabled.	Medium	High	Unit tests will verify that any feature flag or plugin combination still results in our service operational.
See more potential risk examples

For maintainers

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

[sabarasaba]

could we add some comments here on why this replacement needs to be made?

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 5e314ca

Metrics [docs]

Unknown metric groups

ESLint disabled in files

id	before	after	diff
osquery	1	2	+1

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	19	21	+2
fleet	61	67	+6
osquery	108	113	+5
securitySolution	441	447	+6
total			+19

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	20	22	+2
fleet	69	75	+6
osquery	109	115	+6
securitySolution	518	524	+6
total			+20

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

cc @mibragimov

[sabarasaba]

Changes lgtm, tested locally and all headers seem to be correctly sent!

[elasticmachine]

Pinging @elastic/platform-deployment-management (Team:Deployment Management)

[alisonelizabeth]

@mibragimov would you mind updating the PR description when you get a chance to explain why this is only needed for 8.6?

[sabarasaba]

I've added a small section in the summary, but feel free to add more context if you feel like we need to @mibragimov

[paulmakeraiimi]

I have Kibana 8.6.2 and dropped a console.log into the getEntity function to check both the headers and response, and both look fine, yet autocomplete is still not working?