E2E supports VKS data mover environment.

* Add new flag HAS_VSPHERE_PLUGIN for E2E test.
* Modify the E2E README for the new parameter.
* Add the VolumeSnapshotClass for VKS.
* Modify the plugin install logic.
* Modify the cases to support data mover case in VKS.

Signed-off-by: Xun Jiang <xun.jiang@broadcom.com>

test/testdata/volume-snapshot-class/vsphere.yaml

@@ -0,0 +1,13 @@
+---
+apiVersion: snapshot.storage.k8s.io/v1
+deletionPolicy: Delete
+driver: csi.vsphere.vmware.com
+kind: VolumeSnapshotClass
+metadata:
+  annotations:
+    snapshot.storage.kubernetes.io/is-default-class: "true"
+  labels:
+    velero.io/csi-volumesnapshot-class: "true"
+  name: volumesnapshotclass-delete
+parameters:
+  svVolumeSnapshotClass: volumesnapshotclass-delete