Retrieves appliance reachability time series data for monitoring WebSocket connectivity status. Returns portal, orchestrator, and appliance reachability metrics at minute-level (day granularity) or daily-level (month granularity). The data source table and aggregation method changes based on granularity: 'day' uses minuteappliancereachability with raw values, 'month' uses dailyappliancereachability with sumMerge aggregation. Timezone is determined by the appliance's business hour configuration settings.