get_storage: RuntimeDescriptor<
    [address: FixedSizeBinary<20>, key: FixedSizeBinary<32>],
    ResultPayload<
        Binary
        | undefined,
        Enum<{ DoesntExist: undefined; KeyDecodingFailed: undefined }>,
    >,
>

Query a given storage key in a given contract.

Returns Ok(Some(Vec<u8>)) if the storage value exists under the given key in the specified account and Ok(None) if it doesn't. If the account specified by the address doesn't exist, or doesn't have a contract then Err is returned.