cmd/k8s-operator,k8s-operator/apis: set a readiness condition on egress Services
Set a readiness condition on ExternalName Services that define a tailnet target
to route cluster traffic to via a ProxyGroup's proxies. The condition
is set to true if at least one proxy is currently set up to route.
Updates tailscale/tailscale#13406
Signed-off-by: Irbe Krumina <irbe@tailscale.com>
