Use k8s utils pointer instead of Azure autorest/to

Since k/u includes pointer functions which are equivalent to the
autorest/to pointer functions, and the latter are deprecated, it seems
useful to switch to the former:
* to.FooPtr becomes pointer.Foo
* to.Foo becomes pointer.FooDeref with an appropriate default
* to.StringSlicePtr becomes &

This doesn't remove anything from vendor, but it does turn the
dependency into an indirect one, ready to be removed when the rest of
the Azure migration happens.

Signed-off-by: Stephen Kitt <skitt@redhat.com>

pkg/credentialprovider/azure/azure_credentials_test.go

@@ -25,8 +25,8 @@ import (
 
 	"github.com/Azure/azure-sdk-for-go/services/containerregistry/mgmt/2019-05-01/containerregistry"
 	"github.com/Azure/go-autorest/autorest/azure"
-	"github.com/Azure/go-autorest/autorest/to"
 	"k8s.io/client-go/tools/cache"
+	"k8s.io/utils/pointer"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -39,27 +39,27 @@ func Test(t *testing.T) {
     }`
 	result := []containerregistry.Registry{
 		{
-			Name: to.StringPtr("foo"),
+			Name: pointer.String("foo"),
 			RegistryProperties: &containerregistry.RegistryProperties{
-				LoginServer: to.StringPtr("*.azurecr.io"),
+				LoginServer: pointer.String("*.azurecr.io"),
 			},
 		},
 		{
-			Name: to.StringPtr("bar"),
+			Name: pointer.String("bar"),
 			RegistryProperties: &containerregistry.RegistryProperties{
-				LoginServer: to.StringPtr("*.azurecr.cn"),
+				LoginServer: pointer.String("*.azurecr.cn"),
 			},
 		},
 		{
-			Name: to.StringPtr("baz"),
+			Name: pointer.String("baz"),
 			RegistryProperties: &containerregistry.RegistryProperties{
-				LoginServer: to.StringPtr("*.azurecr.de"),
+				LoginServer: pointer.String("*.azurecr.de"),
 			},
 		},
 		{
-			Name: to.StringPtr("bus"),
+			Name: pointer.String("bus"),
 			RegistryProperties: &containerregistry.RegistryProperties{
-				LoginServer: to.StringPtr("*.azurecr.us"),
+				LoginServer: pointer.String("*.azurecr.us"),
 			},
 		},
 	}