Contour deployment should allow for additional customization

[infbase]

Overview of feature request
Contour deployment should allow for additional customization so that it works in clusters with additional constraints or existing configurations.

Additional context
Examples of additional configurations that must be supported (as helm values):

If external load balancers are blocked in AKS (via Azure Policy or Gatekeeper for instance) the load balancer must be annotated to use the internal LB:

envoy:
  service:
    annotations:
        "service.beta.kubernetes.io/azure-load-balancer-internal": "true"

Not being able to set this results in rad env init kubernetes failing in these clusters.

If other ingress controllers exist in the cluster, Contour should not be automatically set to default as that may have an impact on existing services:

contour:
  ingressClass:
    default: false

AB#6986

AB#9690

[infbase]

Current additional annotations needed on the LoadBalancer service, in our case:

    service.beta.kubernetes.io/azure-load-balancer-health-probe-request-path: /healthz
    service.beta.kubernetes.io/azure-load-balancer-internal: "true"
    service.beta.kubernetes.io/azure-load-balancer-internal-subnet: xxx