cmd/containerboot,kube/kubetypes,cmd/k8s-operator: detect if Ingress is created in a tailnet that has no HTTPS
This attempts to make Kubernetes Operator L7 Ingress setup failures more explicit:
- the Ingress resource now only advertises HTTPS endpoint via status.ingress.loadBalancer.hostname when/if the proxy has succesfully loaded serve config
- the proxy attempts to catch cases where HTTPS is disabled for the tailnet and logs a warning
Updates tailscale/tailscale#12079
Updates tailscale/tailscale#10407
Signed-off-by: Irbe Krumina <irbe@tailscale.com>