[aws-cloudwatch-metrics] Ability to control cluster metrics Log Group retention time.

Would be great to be able to set the max retention days for the AWS Log Group that contains all the cluster metrics. By default it's set to "Never Expire" and it will just accumulate lots and lots of metrics and the AWS bill will just increase over time

Start with the aws-cloudwatch-metrics chart and locate the AWS Log Group that stores cluster metrics. Trace how its configuration is defined, then determine where a maximum retention value could be exposed and verify that the resulting Log Group no longer defaults to Never Expire.

Written by the indexing model from the issue text.