WIP: added more ingress gateway support

https://repo1.dso.mil/platform-one/big-bang/bigbang/-/issues/136

Example

extraIngressGateways:
  - name: atoy-super-secret-gateway
  # setting the existing fields
  - name: atoy-super-secret-gateway-2
    k8s:
      serviceAnnotations:
        one: two
      hpaSpec:
        minReplicas: 0
        maxReplicas: 1
  # setting the ports
  - name: atoy-super-secret-gateway-3
    service:
      type: NodePort
      ports:
      - port: 15021
        targetPort: 15021
        name: status-port
        protocol: TCP
        nodePort: 32000

Output

  components:
    ingressGateways:
      - name: istio-ingressgateway
        namespace: default
        enabled: true
        k8s:
          service:
            type: LoadBalancer
            ports:
              -
                name: status-port
                port: 15021
                protocol: TCP
                targetPort: 15021
              -
                name: http2
                port: 80
                protocol: TCP
                targetPort: 8080
              -
                name: https
                port: 443
                protocol: TCP
                targetPort: 8443
              -
                name: tcp-istiod
                port: 15012
                protocol: TCP
                targetPort: 15012
              -
                name: tls
                port: 15443
                protocol: TCP
                targetPort: 15443
          hpaSpec:
            minReplicas: 1
            maxReplicas: 5
            metrics:
              - type: Resource
                resource:
                  name: cpu
                  targetAverageUtilization: 60
            scaleTargetRef:
              apiVersion: apps/v1
              kind: Deployment
              name: istio-ingressgateway
          strategy:
            rollingUpdate:
              maxSurge: 100%
              maxUnavailable: 25%
          serviceAnnotations:
              {}
      - name: atoy-super-secret-gateway
        enabled: true
      - name: atoy-super-secret-gateway-2
        enabled: true
        k8s: 
          hpaSpec:
            minReplicas: 0
            maxReplicas: 1
            metrics:
              - type: Resource
                resource:
                  name: cpu
                  targetAverageUtilization: 60
            scaleTargetRef:
              apiVersion: apps/v1
              kind: Deployment
              name: atoy-super-secret-gateway-2
          strategy:
            rollingUpdate:
              maxSurge: 100%
              maxUnavailable: 25%
          serviceAnnotations:
              one: two
      - name: atoy-super-secret-gateway-3
        enabled: true
        k8s:
          service:
            type: NodePort
            ports:
              -
                name: status-port
                nodePort: 32000
                port: 15021
                protocol: TCP
                targetPort: 15021