Function get_option_chain 

pub async fn get_option_chain(
    client: &FutuClient,
    owner: &Security,
    begin_time: &str,
    end_time: &str,
    option_type: Option<i32>,
    option_cond: Option<i32>,
) -> Result<S2c>

获取期权链（原始 proto 响应）