nfs: Add support for nfs shallow volumes

# Describe the feature you'd like to have #

Add support for nfs shallow volumes based on cephfs shallow volumes
A nfs shallow volume will need to use a different path(/.snap/) to mount volumes on node.

- https://github.com/ceph/ceph-csi/blob/devel/docs/design/proposals/cephfs-snapshot-shallow-ro-vol.md#node-operations
- https://github.com/ceph/ceph-csi/blob/devel/internal/nfs/controller/volume.go#L150C24-L150C24

# What is the value to the end user? (why is it a priority?) #

User will benefit from the same use cases as cephfs https://github.com/ceph/ceph-csi/blob/devel/docs/design/proposals/cephfs-snapshot-shallow-ro-vol.md#use-cases for nfs.

# How will we know we have a good solution? (acceptance criteria) #

nfs shallow volumes should work similar to cephfs shallow volumes.