Rework of cloudwatch configmap

**Is your feature request related to a problem?**
We need to create a special configmap and replace the one from aws-cloudwatch-chart if we need to add a specific configuration to the existing json file as it is not supported.
We are really frustrated by this basic missing functionality which can be resolved in like 15 seconds with simple chart change.
**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**
I want to be able to add more configuration then what are currently listed and it can be achieved by simple enhancement. If you want i can even create you a PR for that.

**Describe alternatives you've considered**
Alternative is that we replace your configmap with your kubernetes manifest but with that we are breaking helm chart functionality and we are doing anti-pattern stuff, but there is no other workaround for this moment. We have to keep it enforced this way even with ArgoCD which is additionaly causing more anti-patterns because of simple missing piece.

Start by inspecting the aws-cloudwatch-metrics Helm chart templates and its current ConfigMap configuration. Determine how additional JSON settings should be supplied and verify that the chart renders a replacement ConfigMap while preserving normal Helm chart functionality.

Written by the indexing model from the issue text.