[feature] Option to set long pooling wait time

[franciscoantonello]

Sometimes when we are moving messages, SQS responds with an empty list of messages (empty receives), even if the queue still has messages to be moved.

Would be nice if we could set the WaitTimeSeconds parameter

	var params = &sqs.ReceiveMessageInput{
		QueueUrl:              aws.String(sourceQueueUrl),
		VisibilityTimeout:     aws.Int64(2),
		WaitTimeSeconds:       aws.Int64(*waitTimeSeconds), // something like this
		MaxNumberOfMessages:   aws.Int64(*maxBatchSize),
		MessageAttributeNames: []*string{aws.String(sqs.QueueAttributeNameAll)},
		AttributeNames: []*string{
			aws.String(sqs.MessageSystemAttributeNameMessageGroupId),
			aws.String(sqs.MessageSystemAttributeNameMessageDeduplicationId)},
	}

Of course, this is just to show the parameter.
We also should create the flag and validations (wait time should be between 0 and 20)