Optimize GetControllerName for CNP.

Use strings.Builder instead of fmt.Sprintf().

Results:
```
benchmark                            old ns/op     new ns/op     delta
BenchmarkCNPGetControllerName-10     338           206           -39.05%

benchmark                            old allocs     new allocs     delta
BenchmarkCNPGetControllerName-10     6              4              -33.33%

benchmark                            old bytes     new bytes     delta
BenchmarkCNPGetControllerName-10     464           432           -6.90%
```

Signed-off-by: Marcel Zieba <marcel.zieba@isovalent.com>

pkg/k8s/apis/cilium.io/v2/cnp_types.go

@@ -6,6 +6,7 @@ package v2
 import (
 	"fmt"
 	"reflect"
+	"strings"
 
 	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -238,7 +239,14 @@ func (r *CiliumNetworkPolicy) Parse() (api.Rules, error) {
 // GetControllerName returns the unique name for the controller manager.
 func (r *CiliumNetworkPolicy) GetControllerName() string {
 	name := k8sUtils.GetObjNamespaceName(&r.ObjectMeta)
-	return fmt.Sprintf("%s (v2 %s)", k8sConst.CtrlPrefixPolicyStatus, name)
+	const staticLen = 6
+	var str strings.Builder
+	str.Grow(staticLen + len(name) + len(k8sConst.CtrlPrefixPolicyStatus))
+	str.WriteString(k8sConst.CtrlPrefixPolicyStatus)
+	str.WriteString(" (v2 ")
+	str.WriteString(name)
+	str.WriteString(")")
+	return str.String()
 }
 
 // GetIdentityLabels returns all rule labels in the CiliumNetworkPolicy.

pkg/k8s/apis/cilium.io/v2/cnp_types_test.go

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright Authors of Cilium
+
+package v2
+
+import (
+	"testing"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func BenchmarkCNPGetControllerName(b *testing.B) {
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		for _, s := range []CiliumNetworkPolicy{
+			{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "test",
+					Namespace: "default",
+				},
+			},
+			{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "longname",
+					Namespace: "",
+				},
+			},
+		} {
+			_ = s.GetControllerName()
+		}
+	}
+}