UPSTREAM: <carry>: Export internal code from k8s.io/apimachinery/pkg/util/managedfields

Some of the code we use in openshift-tests was recently made internal
in kubernetes#115065. This patch
exposes the code we need there.

Author: bertinatto

staging/src/k8s.io/apimachinery/pkg/util/managedfields/patch.go

@@ -0,0 +1,15 @@
+package managedfields
+
+import (
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/managedfields/internal"
+)
+
+// ManagedInterface groups a fieldpath.ManagedFields together with the timestamps associated with each operation.
+type ManagedInterface = internal.ManagedInterface
+
+// DecodeManagedFields converts ManagedFields from the wire format (api format)
+// to the format used by sigs.k8s.io/structured-merge-diff
+func DecodeManagedFields(encodedManagedFields []metav1.ManagedFieldsEntry) (ManagedInterface, error) {
+	return internal.DecodeManagedFields(encodedManagedFields)
+}