Move member VolumeSnapshotContents creation to the sidecar

[leonardoce]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change

/kind bug

/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:

It allows the use of information from the CreateGroupSnapshot RPC call to fill out the status of VolumeSnapshotContents and set the restoreSize field even when the ListSnapshots GRPC call is not implemented.

Which issue(s) this PR fixes:

Fixes #1271

Special notes for your reviewer:

A subsequent PR will thread a context to the function where the member VolumeSnapshotContents are created.

Does this PR introduce a user-facing change?:

The restoreSize field is now set when creating a VolumeGroupSnapshot even if the CSI Driver does not implement the ListSnapshots GRPC call. Starting from this release, the CSI snapshotter sidecar requires RBAC permission to create VolumeSnapshotContents objects.

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[leonardoce]

With this PR, member VolumeSnapshot objects have the restoreSize attribute set even when the ListSnapshot GRPC call is not implemented.

What follows is an example using rook-ceph.cephfs.csi.ceph.com:

apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  creationTimestamp: "2025-04-07T15:19:47Z"
  finalizers:
  - snapshot.storage.kubernetes.io/volumesnapshot-in-group-protection
  - snapshot.storage.kubernetes.io/volumesnapshot-as-source-protection
  generation: 1
  name: snapshot-561edd9357eaf7437ebf35517d7c65dde0835aa172959e822af7224cbf62e1e5
  namespace: default
  ownerReferences:
  - apiVersion: groupsnapshot.storage.k8s.io/v1beta1
    kind: VolumeGroupSnapshot
    name: new-groupsnapshot-demo
    uid: 6fc6c8d9-437a-4cf9-a142-93955cd93292
  resourceVersion: "5554"
  uid: 0c1af52e-9706-41bb-837a-e50ac79b8395
spec:
  source:
    persistentVolumeClaimName: cluster-example-1
status:
  boundVolumeSnapshotContentName: snapcontent-561edd9357eaf7437ebf35517d7c65dde0835aa172959e822af7224cbf62e1e5
  creationTime: "2025-04-07T15:19:44Z"
  readyToUse: true
  restoreSize: 1Gi
  volumeGroupSnapshotName: new-groupsnapshot-demo
---
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotContent
metadata:
  annotations:
    groupsnapshot.storage.k8s.io/volumeGroupSnapshotHandle: 0001-0009-rook-ceph-0000000000000001-a3cb7755-9512-41bc-b330-54621dd0245e
    snapshot.storage.kubernetes.io/deletion-secret-name: rook-csi-cephfs-provisioner
    snapshot.storage.kubernetes.io/deletion-secret-namespace: rook-ceph
  creationTimestamp: "2025-04-07T15:19:44Z"
  finalizers:
  - snapshot.storage.kubernetes.io/volumesnapshotcontent-bound-protection
  generation: 2
  name: snapcontent-561edd9357eaf7437ebf35517d7c65dde0835aa172959e822af7224cbf62e1e5
  resourceVersion: "5549"
  uid: 3a4fd8e4-dc5d-42d9-8825-f2d506ff869b
spec:
  deletionPolicy: Delete
  driver: rook-ceph.cephfs.csi.ceph.com
  source:
    volumeHandle: 0001-0009-rook-ceph-0000000000000001-d251aa4b-679f-4ad4-896c-5b42fdb5bdfd
  volumeSnapshotRef:
    kind: VolumeSnapshot
    name: snapshot-561edd9357eaf7437ebf35517d7c65dde0835aa172959e822af7224cbf62e1e5
    namespace: default
    uid: 0c1af52e-9706-41bb-837a-e50ac79b8395
status:
  creationTime: 1744039184168252000
  readyToUse: true
  restoreSize: 1073741824
  snapshotHandle: 0001-0009-rook-ceph-0000000000000001-3f1acff9-bede-4fd7-92b4-d6f68a0604cf
  volumeGroupSnapshotHandle: 0001-0009-rook-ceph-0000000000000001-a3cb7755-9512-41bc-b330-54621dd0245e

I also tested it using the CSI host path driver with the ListSnapshots GRPC call disabled.