Start fixing err113 issues: add static errors and nolint for tests

- Define ErrTypeConversion static error in common/client.go
- Update import to use apierrors for k8s errors
- Add nolint directives for test files that use dynamic errors for testing

This is the first step in addressing 50 err113 issues. Test files use
dynamic errors to match production error messages, so nolint is appropriate.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: Anand Kumar

pkg/controller/certmanager/credentials_request_test.go

@@ -1,3 +1,4 @@
+//nolint:err113 // test file uses dynamic errors to match production error messages
 package certmanager
 
 import (

pkg/controller/common/client.go

@@ -2,16 +2,22 @@ package common
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"reflect"
 
-	"k8s.io/apimachinery/pkg/api/errors"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/client-go/util/retry"
 
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/manager"
 )
 
+var (
+	// ErrTypeConversion indicates a type conversion failure.
+	ErrTypeConversion = errors.New("failed to convert to client.Object")
+)
+
 // ctrlClientImpl implements the CtrlClient interface using the manager's client.
 type ctrlClientImpl struct {
 	client.Client
@@ -100,7 +106,7 @@ func (c *ctrlClientImpl) UpdateWithRetry(
 		currentInterface := reflect.New(reflect.TypeOf(obj).Elem()).Interface()
 		current, ok := currentInterface.(client.Object)
 		if !ok {
-			return fmt.Errorf("failed to convert to client.Object")
+			return ErrTypeConversion
 		}
 		if err := c.Client.Get(ctx, key, current); err != nil {
 			return fmt.Errorf("failed to fetch latest %q for update: %w", key, err)
@@ -139,7 +145,7 @@ func (c *ctrlClientImpl) Patch(
 
 func (c *ctrlClientImpl) Exists(ctx context.Context, key client.ObjectKey, obj client.Object) (bool, error) {
 	if err := c.Client.Get(ctx, key, obj); err != nil {
-		if errors.IsNotFound(err) {
+		if apierrors.IsNotFound(err) {
 			return false, nil
 		}
 		return false, err

pkg/controller/common/errors_test.go

@@ -1,3 +1,4 @@
+//nolint:err113 // test file uses dynamic errors for simplicity
 package common
 
 import (