feat: cilium configuration overrides for EKS provider

[supershal]

What problem does this PR solve?:

• Stacked on fix: Ciliums kube-proxy replacement rollout and wait #1307 to reuse some functions and reduce merge conflicts.
• Sets Cilium default configuration for EKS to enable eni mode.

Which issue(s) this PR fixes:
Fixes #

How Has This Been Tested?:

• unit test for cilium template rendering

Tested manually for now.

• sample EKS cluster manifest

apiVersion: cluster.x-k8s.io/v1beta1
kind: Cluster
metadata:
  annotations:
    preflight.cluster.caren.nutanix.com/skip: all
  labels:
    cluster.x-k8s.io/provider: eks
  name: shalin-eks
spec:
  topology:
    class: eks-quick-start
    controlPlane:
      metadata:
        annotations:
          controlplane.cluster.x-k8s.io/skip-kube-proxy: ""
    variables:
    - name: clusterConfig
      value:
        addons:
          clusterAutoscaler: {}
          cni:
            provider: Cilium
          csi:
            defaultStorage:
              provider: aws-ebs
              storageClassConfig: default
            providers:
              aws-ebs:
                storageClassConfigs:
                  default: {}
            snapshotController: {}
          nfd: {}
        eks:
          region: us-west-2
    version: v1.32.9
    workers:
      machineDeployments:
      - class: default-worker
        metadata:
          annotations:
            cluster.x-k8s.io/cluster-api-autoscaler-node-group-max-size: "2"
            cluster.x-k8s.io/cluster-api-autoscaler-node-group-min-size: "2"
        name: md-0
        variables:
          overrides:
          - name: workerConfig
            value:
              eks:
                instanceType: m5.2xlarge

• Cilium HCP

apiVersion: addons.cluster.x-k8s.io/v1alpha1
kind: HelmChartProxy
...<redacted>
...
  valuesTemplate: |-
    cni:
      chainingMode: portmap
      exclusive: false
    hubble:
      enabled: true
      tls:
        auto:
          enabled: true               # enable automatic TLS certificate generation
          method: cronJob             # auto generate certificates using cronJob method
          certValidityDuration: 60    # certificates validity duration in days (default 2 months)
          schedule: "0 0 1 * *"       # schedule on the 1st day regeneration of each month
      relay:
        enabled: true
        tls:
          server:
            enabled: true
            mtls: true
        image:
          useDigest: false
        priorityClassName: system-cluster-critical
    ipam:
      mode: eni
    image:
      useDigest: false
    operator:
      image:
        useDigest: false
    certgen:
      image:
        useDigest: false
    socketLB:
      hostNamespaceOnly: true
    envoy:
      image:
        useDigest: false
    kubeProxyReplacement: true
    k8sServiceHost: "A535486E46D73CBF3C959CAE8F6831A4.gr7.us-west-2.eks.amazonaws.com"
    k8sServicePort: "443"
    enableIPv4Masquerade: false
    eni:
      enabled: true
      awsReleaseExcessIPs: true
    routingMode: native
    endpointRoutes:
      enabled: true
  version: 1.17.4
......<redacted>
...
  matchingClusters:
  - apiVersion: cluster.x-k8s.io/v1beta1
    kind: Cluster
    name: shalin-eks
    namespace: default
  observedGeneration: 3

• CNI and all pods running on the cluster

❯ kubectl get pods -A --kubeconfig shalin-eks.conf
NAMESPACE                NAME                                                              READY   STATUS              RESTARTS   AGE
default                  cluster-autoscaler-01997478-76f0-799f-b9ed-ddbff8eab94f-5ffdxsm   0/1     ContainerCreating   0          154m
kube-system              cilium-envoy-2cxcb                                                1/1     Running             0          108m
kube-system              cilium-envoy-nfp4b                                                1/1     Running             0          92m
kube-system              cilium-operator-84796b9ccf-h4lgf                                  1/1     Running             0          108m
kube-system              cilium-operator-84796b9ccf-v5hq4                                  1/1     Running             0          96m
kube-system              cilium-t4grn                                                      1/1     Running             0          92m
kube-system              cilium-zf2zm                                                      1/1     Running             0          108m
kube-system              coredns-5449774944-4hjxt                                          1/1     Running             0          155m
kube-system              coredns-5449774944-78897                                          1/1     Running             0          155m
kube-system              ebs-csi-controller-cb84bcd9-7qtqz                                 6/6     Running             0          154m
kube-system              ebs-csi-controller-cb84bcd9-dn6fg                                 6/6     Running             0          154m
kube-system              ebs-csi-node-m57pl                                                3/3     Running             0          153m
kube-system              ebs-csi-node-nnpcn                                                3/3     Running             0          92m
kube-system              hubble-relay-6b586bc6d-wd7c7                                      1/1     Running             0          108m
kube-system              snapshot-controller-6b6bf6cb95-xrm8q                              1/1     Running             0          154m
node-feature-discovery   node-feature-discovery-gc-6489bd687c-k2psp                        1/1     Running             0          154m
node-feature-discovery   node-feature-discovery-master-6fc5c44fb9-2bddp                    1/1     Running             0          154m
node-feature-discovery   node-feature-discovery-worker-tdv67                               1/1     Running             0          92m
node-feature-discovery   node-feature-discovery-worker-wwr2x                               1/1     Running             0          153m

• cilium-config configmap on EKS cluster updated to reflect eni ipam.
  Special notes for your reviewer:

[dlipovetsky]

There are many difference between the EKS and non-EKS configuration. At what point will we prefer separate templated values (or even separate static values!) for EKS, non-EKS, and possibly some other flavor.