[release-1.17] Reduce mt-broker-controller memory usage with namespaced endpoint informer (#8421)

* Reduce mt-broker-controller memory usage with namespaced endpoint informer

Currently, the mt-broker-controller is using a cluster-wide endpoints
informer but it actually only uses endpoints in the "SYSTEM_NAMESPACE".

Using the namespaced informer factory ensures that the watcher
is only watching endpoints in the `knative-eventing` (also known as
`SYSTEM_NAMESPACE`) namespace.

Signed-off-by: Pierangelo Di Pilato <pierdipi@redhat.com>

* Start informer

Signed-off-by: Pierangelo Di Pilato <pierdipi@redhat.com>

---------

Signed-off-by: Pierangelo Di Pilato <pierdipi@redhat.com>
Co-authored-by: Pierangelo Di Pilato <pierdipi@redhat.com>

go.mod

@@ -1,5 +1,7 @@
 module knative.dev/eventing
 
+// A placeholder comment to rebuild with Go 1.23.5 toolchain to cover CVEs
+
 go 1.22.7
 
 require (

pkg/reconciler/broker/controller.go

@@ -25,11 +25,11 @@ import (
 	"k8s.io/client-go/tools/cache"
 	"knative.dev/pkg/apis"
 	configmapinformer "knative.dev/pkg/client/injection/kube/informers/core/v1/configmap"
-	endpointsinformer "knative.dev/pkg/client/injection/kube/informers/core/v1/endpoints"
 	"knative.dev/pkg/configmap"
 	"knative.dev/pkg/controller"
 	"knative.dev/pkg/injection/clients/dynamicclient"
 	secretinformer "knative.dev/pkg/injection/clients/namespacedkube/informers/core/v1/secret"
+	namespacedinformerfactory "knative.dev/pkg/injection/clients/namespacedkube/informers/factory"
 	"knative.dev/pkg/logging"
 	pkgreconciler "knative.dev/pkg/reconciler"
 	"knative.dev/pkg/resolver"
@@ -69,7 +69,12 @@ func NewController(
 	logger := logging.FromContext(ctx)
 	brokerInformer := brokerinformer.Get(ctx)
 	subscriptionInformer := subscriptioninformer.Get(ctx)
-	endpointsInformer := endpointsinformer.Get(ctx)
+
+	endpointsInformer := namespacedinformerfactory.Get(ctx).Core().V1().Endpoints()
+	if err := controller.StartInformers(ctx.Done(), endpointsInformer.Informer()); err != nil {
+		logger.Fatalw("Failed to start namespaced endpoints informer", zap.Error(err))
+	}
+
 	configmapInformer := configmapinformer.Get(ctx)
 	secretInformer := secretinformer.Get(ctx)
 	eventPolicyInformer := eventpolicyinformer.Get(ctx)