fix: cloudfront request metric is using an invalid statistic

[iliapolo]

The Requests metric that CloudFront emits should use the Sum statistic, not Average.

See Requests in https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/programming-cloudwatch-metrics.html#cloudfront-metrics-distribution-values

In addition, change the period of the CloudFront metrics in the overview dashboard to 1 day (from 5 minutes):

• We usually like to talk about "requests per day" to asses usage, over "requests per 5 minutes".
• It allows for easier trend detection when looking at a large window.

Before

After

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