Agenda: StorageDescriptor<[Key: number], ({
    call: PreimagesBounded;
    maybe_id?: FixedSizeBinary<32>;
    maybe_periodic?: FixedSizeArray<2, number>;
    origin: PolkadotRuntimeOriginCaller;
    priority: number;
} | undefined)[], false, never>

Items to be executed, indexed by the block number that they should be executed on.