Migrate analytics_unique_visits_data to use Metric Instrumentation class

This metric will probably use RedisHllMetric.

https://docs.gitlab.com/ee/development/service_ping/metrics_instrumentation.html#migrate-service-ping-metrics-to-instrumentation-classes

https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/usage_data.rb#L648

      def analytics_unique_visits_data
        results = ::Gitlab::Analytics::UniqueVisits.analytics_events.each_with_object({}) do |target, hash|
          hash[target] = redis_usage_data { unique_visit_service.unique_visits_for(targets: target) }
        end
        results['analytics_unique_visits_for_any_target'] = redis_usage_data { unique_visit_service.unique_visits_for(targets: :analytics) }
        results['analytics_unique_visits_for_any_target_monthly'] = redis_usage_data { unique_visit_service.unique_visits_for(targets: :analytics, **monthly_time_range) }

        { analytics_unique_visits: results }
      end

Testing

Update and ensure that the related tests are passing.