Verify that when a volume policy specifies snapshotClass, the CSI
plugin creates a VolumeSnapshot using that VolumeSnapshotClass. The
test uses a VSC without the velero label to confirm selection comes
from the volume policy parameter, not the label-based fallback.
Ref: #8807
Signed-off-by: Shubham Pampattiwar <spampatt@redhat.com>