Enable curator to delete old log data

What does this MR do?

The official Elastic Stack charts provides Curator, which we now use to expire old indexes after 15 days. Indeed, Filebeat writes data into ES using date based indexes such as filebeat-6.7.0-2020.01.14. We can then easily filter these in curator.

Note: No changelog as this is behind a private feature flag.

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

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