Use direct AWS EKS AMI instead of SkS custom-build

We have stopped building our own custom EKS AMI. As of now we directly rely on the upstream, AWS-provided image for EKS.

One of the main reasons for our custom build was the inclusion of our Teleport node agent, to allow audited SSH access for debugging. However the same functionality can be achieved via AWS SSM.

This has no direct impact for our customers. However on Skyscrapers’ side, we remove complexity and additional AMI storage costs.