refactor(notification): use new queue package (#9360)

# Which Problems Are Solved

The recently introduced notification queue have potential race conditions.

# How the Problems Are Solved

Current code is refactored to use the queue package, which is safe in
regards of concurrency.

# Additional Changes

- the queue is included in startup
- improved code quality of queue

# Additional Context

- closes https://github.com/zitadel/zitadel/issues/9278

internal/notification/channels/instrumenting/logging.go

@@ -13,7 +13,7 @@ func logMessages(ctx context.Context, channel channels.NotificationChannel) chan
 	return channels.HandleMessageFunc(func(message channels.Message) error {
 		logEntry := logging.WithFields(
 			"instance", authz.GetInstance(ctx).InstanceID(),
-			"triggering_event_type", message.GetTriggeringEvent().Type(),
+			"triggering_event_type", message.GetTriggeringEventType(),
 		)
 		logEntry.Debug("sending notification")
 		err := channel.HandleMessage(message)

internal/notification/channels/instrumenting/metrics.go

@@ -24,7 +24,7 @@ func countMessages(ctx context.Context, channel channels.NotificationChannel, su
 
 func addCount(ctx context.Context, metricName string, message channels.Message) {
 	labels := map[string]attribute.Value{
-		"triggering_event_type": attribute.StringValue(string(message.GetTriggeringEvent().Type())),
+		"triggering_event_type": attribute.StringValue(string(message.GetTriggeringEventType())),
 	}
 	addCountErr := metrics.AddCount(ctx, metricName, 1, labels)
 	logging.WithFields("name", metricName, "labels", labels).OnError(addCountErr).Error("incrementing counter metric failed")