Create new rake task with Advanced Search integration details

What does this MR do and why?

This MR adds a new rake task called gitlab:elastic:info that outputs debugging information for the Advanced Search integration.

Screenshots or screen recordings

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #340437 (closed)