Update VolumeSnapshot and VolumeSnapshotContent using JSON patch

fix unit tests

operate on cloned copy

revert to update call for removeSnapshotFinalizer

fix content delete finalizer

pkg/common-controller/snapshot_finalizer_test.go

@@ -17,10 +17,9 @@ limitations under the License.
 package common_controller
 
 import (
-	"testing"
-
 	"github.com/kubernetes-csi/external-snapshotter/v6/pkg/utils"
 	v1 "k8s.io/api/core/v1"
+	"testing"
 )
 
 // Test single call to ensurePVCFinalizer, checkandRemovePVCFinalizer, addSnapshotFinalizer, removeSnapshotFinalizer