[Feature request] Update api generation

[Mister-Hope]

Ts 4.4 introduce a new flag --exactOptionalPropertyTypes, and it's already on stable channel.

See https://devblogs.microsoft.com/typescript/announcing-typescript-4-4/#exact-optional-property-types

With this option,

interface Person {
    name: string,
    age?: number | undefined;
}

and

interface Person {
    name: string,
    age?: number;
}

won't be the same.

Which means all the opitional option should be extra announced with | undefined if it could be. Other wise code like following will be regarded as an error with --exactOptionalPropertyTypes

E.g.: we can pass title: undefined to the following api

let title: string | undefined;

// somehow set title only in some condfitions

wx.showLoading({ title });
// 不能将类型“string | undefined”分配给类型“string”。
//   不能将类型“undefined”分配给类型“string”。ts(2322)

So we should generate the option to:

// before
    interface ShowLoadingOption {
        /** 提示的内容 */
        title: string
        /** 接口调用结束的回调函数（调用成功、失败都会执行） */
        complete?: ShowLoadingCompleteCallback
        /** 接口调用失败的回调函数 */
        fail?: ShowLoadingFailCallback
        /** 是否显示透明蒙层，防止触摸穿透 */
        mask?: boolean
        /** 接口调用成功的回调函数 */
        success?: ShowLoadingSuccessCallback
    }

// after

    interface ShowLoadingOption {
        /** 提示的内容 */
        title: string | undefined
        /** 接口调用结束的回调函数（调用成功、失败都会执行） */
        complete?: ShowLoadingCompleteCallback | undefined
        /** 接口调用失败的回调函数 */
        fail?: ShowLoadingFailCallback | undefined
        /** 是否显示透明蒙层，防止触摸穿透 */
        mask?: boolean | undefined
        /** 接口调用成功的回调函数 */
        success?: ShowLoadingSuccessCallback | undefined
    }