[aws-cloudwatch-metrics] Possibility to add extra envs into container template

**Is your feature request related to a problem?**
I've encountered a problem when pod has to connect to AWS Cloudwatch through proxy. Chart does not support adding extra container envs for http and https proxy URL's.

**Is your feature request related to a specific Helm chart, if yes mention name of the chart?**
aws-cloudwatch-metrics

**Describe the solution you'd like**
able to add extra envs to daemonset chart

**Describe alternatives you've considered**
Right now I'm running a script, using `kubectl set env` option, to inject http and https proxy URL variables after deployment. I understand that I could fork the chart and make the appropriate changes myself, but I think an upstream approach would be better.

Start with the aws-cloudwatch-metrics Helm chart and locate the DaemonSet container template. Determine how the chart should accept extra HTTP and HTTPS proxy environment variables, then verify that a rendered deployment includes those variables.

Written by the indexing model from the issue text.