Add provider eks for template cluster

[calvix]

towards giantswarm/roadmap#2609
Adding a very basic template of a cluster for provider eks this is mostly needed now for internal testing for teams,

No custom EKS values for now, all changes to config maps must be done manually

 #: kubectl gs template cluster --provider=eks --name vac1eks --organization=giantswarm
---
apiVersion: v1
data:
  values: |
    metadata:
      name: vac1eks
      organization: giantswarm
kind: ConfigMap
metadata:
  creationTimestamp: null
  labels:
    giantswarm.io/cluster: vac1eks
  name: vac1eks-userconfig
  namespace: org-giantswarm
---
apiVersion: application.giantswarm.io/v1alpha1
kind: App
metadata:
  labels:
    app-operator.giantswarm.io/version: 0.0.0
  name: vac1eks
  namespace: org-giantswarm
spec:
  catalog: cluster
  config:
    configMap:
      name: ""
      namespace: ""
    secret:
      name: ""
      namespace: ""
  kubeConfig:
    context:
      name: ""
    inCluster: true
    secret:
      name: ""
      namespace: ""
  name: cluster-eks
  namespace: org-giantswarm
  userConfig:
    configMap:
      name: vac1eks-userconfig
      namespace: org-giantswarm
  version: 0.3.2
---
apiVersion: v1
data:
  values: |
    clusterName: vac1eks
    organization: giantswarm
kind: ConfigMap
metadata:
  creationTimestamp: null
  labels:
    giantswarm.io/cluster: vac1eks
  name: vac1eks-default-apps-userconfig
  namespace: org-giantswarm
---
apiVersion: application.giantswarm.io/v1alpha1
kind: App
metadata:
  labels:
    app-operator.giantswarm.io/version: 0.0.0
    giantswarm.io/cluster: vac1eks
    giantswarm.io/managed-by: cluster
  name: vac1eks-default-apps
  namespace: org-giantswarm
spec:
  catalog: cluster
  config:
    configMap:
      name: vac1eks-cluster-values
      namespace: org-giantswarm
    secret:
      name: ""
      namespace: ""
  kubeConfig:
    context:
      name: ""
    inCluster: true
    secret:
      name: ""
      namespace: ""
  name: default-apps-eks
  namespace: org-giantswarm
  userConfig:
    configMap:
      name: vac1eks-default-apps-userconfig
      namespace: org-giantswarm
  version: 0.1.2

[anvddriesch]

lgtm