api: encode NamespacedName with lower case in JSON

That is how a workaround in controller-runtime has encoded
NamespacedName (https://github.com/kubernetes-sigs/controller-runtime/blob/a33d038b84d0e7f615b8d803bdc47f0d1f8484b7/pkg/log/zap/kube_helpers.go#L49-L57)
and it is also more consistent with Kubernetes API standards.

The namespace can be left out.

Returning an anonymous struct in MarshalLog makes it impossible for
controller-runtime to adapt the type and thus blocks updating
controller-runtime to Kubernetes 1.27 because log content would
change.

Kubernetes-commit: f564f7a3559a2710b879122dd81b536fc930c410

pkg/types/namespacedname.go

@@ -41,7 +41,8 @@ func (n NamespacedName) String() string {
 // MarshalLog emits a struct containing required key/value pair
 func (n NamespacedName) MarshalLog() interface{} {
 	return struct {
-		Name, Namespace string
+		Name      string `json:"name"`
+		Namespace string `json:"namespace,omitempty"`
 	}{
 		Name:      n.Name,
 		Namespace: n.Namespace,