Implement scan() for cluster mode

[ikolomi]

Although Jedis drive does not implement public ValkeyGlideKeyCommands::public Cursor<byte[]> scan(ScanOptions options) for cluster mode, Lettuce does. Valkey-Glide also supports scanning in cluster mode but currently ValkeyGlideClusterConnectionTests::scanShouldReturnAllKeys fails, as no keys are returned. Falling back to much the Jedis implementation.