Support CSI Snapshot for legacy PVCs and PVs

[0xLeo258]

Is your feature request related to a problem?/Why is this needed

The remaining PVCs and PVs that are still configured with the legacy in-tree StorageClass, where the provisioner is set to kubernetes.io/aws-ebs rather than the newer ebs.csi.aws.com.

While these persistent volumes should have been automatically migrated to the CSI driver using the annotation-based migration feature, CSI snapshot doesn't work on them.

Describe the solution you'd like in detail

Add an edge case(draft below) to enable creating VolumeSnapshotContent for CSI annotated PV

isPVMigratedToCSI := func(pv *corev1api.PersistentVolume) bool {
	if pv == nil || pv.Annotations == nil {
		return false
	}
	migratedTo, ok := pv.Annotations["pv.kubernetes.io/migrated-to"]
	return ok && strings.Contains(strings.ToLower(migratedTo), "csi")
}

Describe alternatives you've considered

N/A
Additional context

N/A