cmd/k8s-operator: ProxyClass annotation for Services and Ingresses (#16363)

* cmd/k8s-operator: ProxyClass annotation for Services and Ingresses

Previously, the ProxyClass could only be configured for Services and
Ingresses via a Label. This adds the ability to set it via an
Annotation, but prioritizes the Label if both a Label and Annotation are
set.

Updates #14323

Signed-off-by: chaosinthecrd <tom@tmlabs.co.uk>

* Update cmd/k8s-operator/operator.go

Co-authored-by: Tom Proctor <tomhjp@users.noreply.github.com>
Signed-off-by: Tom Meadows <tom@tmlabs.co.uk>

* Update cmd/k8s-operator/operator.go

Signed-off-by: Tom Meadows <tom@tmlabs.co.uk>

* cmd/k8s-operator: ProxyClass annotation for Services and Ingresses

Previously, the ProxyClass could only be configured for Services and
Ingresses via a Label. This adds the ability to set it via an
Annotation, but prioritizes the Label if both a Label and Annotation are
set.

Updates #14323

Signed-off-by: chaosinthecrd <tom@tmlabs.co.uk>

---------

Signed-off-by: chaosinthecrd <tom@tmlabs.co.uk>
Signed-off-by: Tom Meadows <tom@tmlabs.co.uk>
Co-authored-by: Tom Proctor <tomhjp@users.noreply.github.com>

cmd/k8s-operator/ingress.go

@@ -34,6 +34,7 @@ const (
 	tailscaleIngressClassName      = "tailscale"                                   // ingressClass.metadata.name for tailscale IngressClass resource
 	tailscaleIngressControllerName = "tailscale.com/ts-ingress"                    // ingressClass.spec.controllerName for tailscale IngressClass resource
 	ingressClassDefaultAnnotation  = "ingressclass.kubernetes.io/is-default-class" // we do not support this https://kubernetes.io/docs/concepts/services-networking/ingress/#default-ingress-class
+	indexIngressProxyClass         = ".metadata.annotations.ingress-proxy-class"
 )
 
 type IngressReconciler struct {