Migrate `manila.csi.openstack.org` StorageClass to using `nfs.manila.csi.openstack.org`

[mnaser]

The old storage classes were created with a CSIDriver that did not have a prefix of the protocol type, where as the new ones are using NFS and the correct prefix.

We should simply make it so that the old ones are dropped and replaced by the new ones as part of this.

[ricolin]

@mnaser @okozachenko1203
The upgrade is stuck with existing PVs that already have "provisioner" defined and which cannot be easily modified.
For this, I propose a pr #748 to use a different storage class so no upgrade conflict.
And for cluster that necessary to upgrade, we can come out with an migration guide in docs. WDYT?

[ricolin]

for manual upgrade guide,
I'm thinking of using persistentVolumeReclaimPolicy: Retain for pv and update SC's provioner name + delete and recreate pv, PVC