Implement a percentage based rollout for ElasticSearch

What does this MR do?

Related to #33681 (closed)

Provide API endpoints to rollout Elasticsearch to namespaces, scoped by plan.

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