Implement VolumeSnapshot IRI methods in volume poollet & broker

[sujeet01]

Proposed Changes

• Volume Snapshot Controller: Implemented in volumepoollet for managing the full lifecycle of VolumeSnapshots.
• Volume Broker IRI Methods: Implemented CreateVolumeSnapshot, DeleteVolumeSnapshot, and ListVolumeSnapshots with proper gRPC status handling.
• VolumeSnapshotRef Field Indexer: Added field indexing in the volume controller for faster lookups when volumes reference snapshots.
• Volume Restoration Flow: Added support for creating volumes from snapshots with correct data source handling.
• Encryption Inheritance: Added encryption inheritance logic for volumes created from snapshots of encrypted volumes.
• Error Handling: Enhanced error handling for missing encryption secrets, source volumes, and snapshots with proper gRPC status codes
• Downward API Support: Added downward API labels support for VolumeSnapshot resource.
• ImageDataSource Support: Added ImageDataSource handling with backward compatibility for soon-to-be-deprecated spec.image field.
• Test Coverage: Added comprehensive test cases for VolumeSnapshot lifecycle, restoration flow, and encryption scenarios.

Fixes #1344 #1345