OutboundLanes: StorageDescriptor<[Key: FixedSizeBinary<4>], {
    latest_generated_nonce: bigint;
    latest_received_nonce: bigint;
    oldest_unpruned_nonce: bigint;
    state: Enum<{
        Closed: undefined;
        Opened: undefined;
    }>;
}, true, never>

Map of lane id => outbound lane data.