Add VSA aggregation status to GraphQL

What does this MR do and why?

This MR exposes the VSA aggregation status via GraphQL. Example queries:

{
  group(fullPath: "gitlab-org") {
    valueStreamAnalytics {
      aggregationStatus {
        enabled
        lastUpdateAt
        estimatedNextUpdateAt
      }
    }
  }
}

{
  project(fullPath: "gitlab-org/gitlab") {
    valueStreamAnalytics {
      aggregationStatus {
        enabled
        lastUpdateAt
        estimatedNextUpdateAt
      }
    }
  }
}

Note: The aggregation always happens via the root ancestor in VSA thus projects and groups in the hierarchy share the same aggregation record.

MR acceptance checklist

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Related to #410342 (closed)