prow-build-cluster: deploy cluster-autoscaler, metrics-server, and AWS Secrets Manager integration

[xmudrii]

Based on requirements stated in #4686, this PR ensures we deploy the following components in prow-build-cluster:

• cluster-autoscaler
• metrics-server
• secrets-store-csi-driver and secrets-store-csi-driver-provider-aws (to provide AWS Secrets Manager integration)

All components are fully-managed by Terraform. Kubernetes YAML manifests were converted to Terraform (.tf) files using tfk8s and deployed using the hashicorp/kubernetes provider. Helm charts are reconciled using the hashicorp/helm provider.

IRSA (IAM role for Service Account) for Secrets Manager is commented and provided as a reference. It's supposed to uncommented and updated based on what we want to use the Secrets Manager for.

The reason for going with Terraform for everything is to:

• avoid additional Bash scripts -- we deploy everything with a single terraform apply invocation
• make it easy to replicate this setup and eventually deploy additional build clusters

This change is already reconciled. Additionally, the all three components were tested and are working well.

/assign @ameukam @upodroid

[ameukam]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ameukam, xmudrii

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• infra/aws/OWNERS [ameukam]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment