feat: initialize configuration and enhance IPC handling in task runner tests

- Added configuration initialization in db.go to ensure proper setup of application settings.
- Refactored runner_test.go to streamline IPC message handling by introducing a setupPipe function and an initRunner function for better readability and maintainability.
- Improved synchronization in tests by using channels for signaling readiness and processing, enhancing the reliability of IPC message handling.
- Updated test cases to validate IPC message processing and error handling, ensuring robustness in the task runner's functionality.

Author: Marvin Zhang

core/mongo/db.go

@@ -1,10 +1,15 @@
 package mongo
 
 import (
+	"github.com/crawlab-team/crawlab/core/config"
 	"github.com/spf13/viper"
 	"go.mongodb.org/mongo-driver/mongo"
 )
 
+func init() {
+	config.InitConfig()
+}
+
 func GetMongoDb(dbName string) *mongo.Database {
 	// Use default database name if not provided
 	if dbName == "" {