Add environmental variable to determine the agent's cluster name

[musa-asad]

Description of the issue

When running on a Kubernetes cluster, the only way the CloudWatch Agent can detect the cluster name is:

1. If it's provided in the configuration:

"kubernetes": {
  "cluster_name": "<cluster-name>",
  "enhanced_container_insights": true
},
"application_signals": {
  "hosted_in": "<cluster-name>"
}

2. By making a ec2:DescribeTags call.

Ideally, the agent should minimize external API calls, so we should implement a global way to retrieve the cluster name in case it isn't provided in the configuration. The Amazon CloudWatch Observability EKS add-on / Helm chart includes a .Values.clusterName, which can be passed in as an environmental variable for the agent's pod.

Description of changes

Important

Co-PR: aws/amazon-cloudwatch-agent#1525

• Add K8S_CLUSTER_NAME with cluster name from received from .Values.clusterName.

License

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Tests

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