Add a simple elasticsearch API test

What does this MR do?

Adds API only test for elasticsearch. Creates a project that is private by default, adds a known blob to a README.md then uses elastic search to look for that blob as both an authorized user, expecting success, and an unauthorized user, expecting empty results to be returned. TODO:

• verify elastic search is on, if not turn it on
• add step to ping the es url in order to fail faster if it's not up (requires us to know how long it takes to start the es service in CI which is currently unknown to me)
• add check to verify blob was found in proper project

see issue https://gitlab.com/gitlab-org/gitlab/issues/202161

Closes https://gitlab.com/gitlab-org/gitlab/issues/202161

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team