Add finalizer to prevent deletion of individual volume snapshots

[RaunakShah]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This PR adds a finaliser to volume snapshot objects that are part of a group snapshot. The finaliser is removed if the group snapshot is deleted.
This is to prevent individual snapshots from being deleted when the group snapshot still exists

Testing

Create a group snapshot:

% kubectl get vgs
NAME                READYTOUSE   VOLUMEGROUPSNAPSHOTCLASS   VOLUMEGROUPSNAPSHOTCONTENT                              CREATIONTIME   AGE
my-group-snapshot   true         vgs-class                  groupsnapcontent-eb950570-7be9-41c6-a1aa-363d20019095   3s             3s
% kubectl get vs
NAME                                                                                           READYTOUSE   SOURCEPVC   SOURCESNAPSHOTCONTENT                                                                             RESTORESIZE   SNAPSHOTCLASS   SNAPSHOTCONTENT                                                                                   CREATIONTIME   AGE
snapshot-16f64470380b9fadfd5c37aefd2169e56cdd59dbe6c36a3fd1f5cba8203e9241-2023-12-07-12.20.9   true                     snapcontent-16f64470380b9fadfd5c37aefd2169e56cdd59dbe6c36a3fd1f5cba8203e9241-2023-12-07-12.20.9   1Gi                           snapcontent-16f64470380b9fadfd5c37aefd2169e56cdd59dbe6c36a3fd1f5cba8203e9241-2023-12-07-12.20.9   11s            11s
snapshot-cfb80f3c4fe5ad13011e84ed233998ebc58c13b80d7d9c70915cf342d823cf68-2023-12-07-12.20.9   true                     snapcontent-cfb80f3c4fe5ad13011e84ed233998ebc58c13b80d7d9c70915cf342d823cf68-2023-12-07-12.20.9   1Gi                           snapcontent-cfb80f3c4fe5ad13011e84ed233998ebc58c13b80d7d9c70915cf342d823cf68-2023-12-07-12.20.9   11s            11s

Delete a volume snapshot and view events:

% kubectl delete vs snapshot-16f64470380b9fadfd5c37aefd2169e56cdd59dbe6c36a3fd1f5cba8203e9241-2023-12-07-12.20.9
'volumesnapshot.snapshot.storage.k8s.io "snapshot-16f64470380b9fadfd5c37aefd2169e56cdd59dbe6c36a3fd1f5cba8203e9241-2023-12-07-12.20.9" deleted
^C
% kubectl describe vs snapshot-16f64470380b9fadfd5c37aefd2169e56cdd59dbe6c36a3fd1f5cba8203e9241-2023-12-07-12.20.9
...
Events:
  Type     Reason                 Age              From                 Message
  ----     ------                 ----             ----                 -------
  Normal   SnapshotCreated        38s              snapshot-controller  Snapshot default/snapshot-16f64470380b9fadfd5c37aefd2169e56cdd59dbe6c36a3fd1f5cba8203e9241-2023-12-07-12.20.9 was successfully created by the CSI driver.
  Normal   SnapshotReady          38s              snapshot-controller  Snapshot default/snapshot-16f64470380b9fadfd5c37aefd2169e56cdd59dbe6c36a3fd1f5cba8203e9241-2023-12-07-12.20.9 is ready to use.
  Warning  SnapshotDeletePending  2s (x3 over 5s)  snapshot-controller  deletion of the individual volume snapshot default/snapshot-16f64470380b9fadfd5c37aefd2169e56cdd59dbe6c36a3fd1f5cba8203e9241-2023-12-07-12.20.9 is not allowed as it belongs to group snapshot default/my-group-snapshot. Deleting the group snapshot will trigger the deletion of all the individual volume snapshots that are part of the group

Delete group snapshot and validate that all resources are deleted:

% kubectl delete -f volumegroupsnapshot-example.yaml 
volumegroupsnapshot.groupsnapshot.storage.k8s.io "my-group-snapshot" deleted
% kubectl get vgs
No resources found in default namespace.
% kubectl get vgsc
No resources found
% kubectl get vs
No resources found in default namespace.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Add finalizer to prevent deletion of individual volume snapshots that are part of a group

[xing-yang]

Can you fix the unit test failure?

[xing-yang]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RaunakShah, xing-yang

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