chore: add retry logic to finalizer operations to prevent update conflicts

[rafatio]

What type of PR is this?
/kind bug

What this PR does / why we need it:
This PR adds retry logic to finalizer operations in the snapshot controller to handle concurrent resource updates gracefully and prevent "object has been modified" errors.

In environments with high concurrency the snapshot controller frequently encounters update conflicts when adding finalizers to VolumeSnapshots and PersistentVolumeClaims. This results in warning events during snapshot creation:

Warning SnapshotFinalizerError VolumeSnapshot/snapshot-example-pvc Failed to check and update snapshot: snapshot controller failed to update namespace/snapshot-example-pvc on API server: Operation cannot be fulfilled on volumesnapshots.snapshot.storage.k8s.io "snapshot-example-pvc": the object has been modified; please apply your changes to the latest version and try again

Warning SnapshotContentCreationFailed VolumeSnapshot/snapshot-example-pvc Failed to create snapshot content with error snapshot controller failed to update example-pvc on API server: Operation cannot be fulfilled on persistentvolumeclaims "example-pvc": the object has been modified; please apply your changes to the latest version and try again

While snapshots eventually succeed after retries at the reconciliation loop level, these errors cause unnecessary event noise and delays.

Solution:

• Wrap finalizer add operations in retry.RetryOnConflict to automatically retry on update conflicts
• Refetch resources from the API server on each retry attempt to ensure updates are based on the latest resource version
• Add checks to detect if finalizers already exist before attempting to add them
• This aligns with Kubernetes best practices for handling concurrent updates

Which issue(s) this PR fixes:

Does this PR introduce a user-facing change?:

Fixed warning events during VolumeSnapshot creation caused by concurrent updates when adding finalizers to PersistentVolumeClaims and VolumeSnapshots.

[k8s-ci-robot]

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[k8s-ci-robot]

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