SQS DLQ alarm should treat missing data as not breaching

[chrishanline]

https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-monitoring-using-cloudwatch.html

When an Amazon SQS queue is inactive for more than six hours, the Amazon SQS service is considered asleep and stops delivering metrics to the CloudWatch service. Missing data, or data representing zero, can't be visualized in the CloudWatch metrics for Amazon SQS for the time period that your Amazon SQS queue was inactive.

Because of this, the DLQ alarms currently created by lift will show Insufficient data most of the time when the queue they monitor are empty and inactive.

This PR sets treatMissingData to notBreaching on the alarm vs the current CDK default of missing. notBreaching will allow an inactive (and thus empty) SQS queue to show Ok when browsing alarms.

[mnapoli]

Thank you!