Switch EKS ci from eksctl to tofu modules

[noahpb]

Description

Currently, our IaC for provisioning EKS clusters in CI uses a combination of eksctl and tofu. We've observed that the current eksctl setup is prone to error and often leaves orphaned resources. Additionally, these tasks run serially which adds considerable time to our CI runs.

We should switch our cluster (and its dependencies) from eksctl to tofu and combine it with the existing IaC for UDS Core dependencies. Internal modules should be used where appropriate.

Related Issues

Relates to #784

[mjnagel]

We should also leverage the approved/reference IAC here for this (I believe that lives here). This would align us with the "golden paths" in our testing.

[joelmccoy]

I would really like to use this as an opportunity to migrate core over to the spacelift environment. Would love to pair with y'all to find the best path forward for you all.

Also using the golden IAC modules will get you up an running super quick. Here is a simple example repo that gets you a full EKS cluster with minimal actual tofu code.

[mjnagel]

Also linking new repo for ref deployment: https://github.com/defenseunicorns/uds-aws-eks-reference-deployment/tree/chore/copy-from-opinionated-modules-branch