[feature] Parametrize cluster add-on CNI name

[seifrajhi]

Current Behavior:

The current configuration hard codes the Cluster Network Infrastructure (CNI) name in the cluster_addons section, making it less flexible for users who wish to use a different CNI plugin.

cluster_addons:
  coredns:
    most_recent: true
  kube-proxy:
    most_recent: true
  vpc-cni:
    most_recent: true

Desired Behavior:

Allow users to parametrize the CNI name or specify a custom CNI plugin in the cluster_addons section.

In this case, I would like to be able to use a variable for the Cilium CNI, which we can set as {{ .variables.cni }}, to either use vpc-cni or installing another CNI using GitOps i.e argoCD

Therefore, like in the module aws-ia/eks-blueprints-addons/aws which gives possibility to install CNI cilium as a helm release