Fix EKS cluster detection

[musa-asad]

Description of the issue

To detect whether the CloudWatch Agent is running on EKS, we look for a ConfigMap named aws-auth, which is only supported for EKS and maps IAM users/roles to K8s RBAC for API access. However, aws-auth is now deprecated and isn't created on new EKS clusters, which marks the CloudWatch Agent as running on native K8s, not EKS, which is not accurate.

Historically, the server version of an EKS cluster has always contained "eks" (e.g. v1.31.4-eks-2d5f260). We can rely on checking the server version instead of the aws-auth ConfigMap. Based on https://gallery.ecr.aws/eks-distro/kubernetes/kube-apiserver, all previous EKS versions include "eks" in them, so it's a reliable mechanism.

Relevant issue: #1249.

Description of changes

• Remove logic to query API server for aws-auth.
• Add logic to query API server for server version.
• Update unit tests to reflect changes.
  • resetTestState() forces re-evaluation of the IsEKS() singleton for each test.

License

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Tests

Before

After

For testing, added a debug line:

Requirements

Before commit the code, please do the following steps.

1. Run make fmt and make fmt-sh
2. Run make lint