Refactor speed notification and add outbound stats

Add OutboundTrafficStat DTO and a CoreServiceManager.queryAllOutboundTrafficStats() method to fetch/reset all outbound counters in one core call and parse Go-side payload. Remove ProfileItem.getAllOutboundTags() and simplify NotificationManager API (startSpeedNotification()/stopSpeedNotification()) to use aggregated stats via the new core query. Replace per-tag polling with a single aggregated update loop (updateSpeedNotificationOnce) to reduce IPC and CPU usage, and update CoreServiceManager call sites accordingly.