refactor：将DataLoaderService中的LoadAll*Async方法移到对应的管理服务中

- 将LoadAllDevicesAsync方法移到DeviceManagementService
 - 将LoadAllVariableTablesAsync方法移到VariableTableManagementService
 - 将LoadAllVariablesAsync方法移到VariableManagementService
 - 将LoadAllMenusAsync方法移到MenuManagementService
 - 将LoadAllMqttServersAsync方法移到MqttManagementService
 - 将LoadAllNlogsAsync方法移到LogManagementService
 - 更新DataLoaderService以使用管理服务提供的方法
 - 修改IDataLoaderService接口以移除这些方法
 - 保持与LoadAllTriggersAsync相同的模式
 - 遵循单一职责原则，提高代码一致性" (提交修改并添加描述性的提交信息)

DMS.Application/Interfaces/Management/IMqttManagementService.cs

@@ -19,4 +19,9 @@ public interface IMqttManagementService
     Task<MqttServer> GetMqttServerByIdAsync(int id);
     Task<int> UpdateMqttServerAsync(MqttServer mqttServer);
     Task<int> UpdateMqttServersAsync(List<MqttServer> mqttServers);
+
+    /// <summary>
+    /// 异步加载所有MQTT服务器数据到内存中。
+    /// </summary>
+    Task LoadAllMqttServersAsync();
 }