Resolve "Add a rake task to create a new ElasticSearch index"

What does this MR do?

This MR adds a new optional parameter index_name to the following rake tasks:

• gitlab:elastic:create_empty_index
• gitlab:elastic:delete_index
• gitlab:elastic:recreate_index

This parameter is useful when one needs to create additional indices such as when a re-index needs to happen.

Related to #213918 (closed)

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

This MR adds testing around the new index_name parameter.

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

Closes #214357 (closed)