feature: Variadic generic packs and mapping expansion

還沒有人認領這個 Issue。

#1861

This feature request requests variadic generics functionality, as well as mapping those generics. My proposed implementation of this feature request would allow the following example syntax:
```lua
---@generic R, T...
---@param fn fun(...: T...):R
---@param ... Component
---@return System
function System.new(fn, ...)
...
end

---@generic R
---@param System self
---@param entities Entity[]
---@return R[]
function System:run()
...
end
```

The example code above also introduces a shorthand for variadics (line 3): whenever the parameter `...` would have an unexpanded parameter pack as an argument, it is implicitly expanded. Any type can be expanded at any point by suffixing a `...`, as shown in line 2.

The motivation of this request arises from an well-typed ECS implementation with object-oriented systems. Without variadic generics, it is not possible in any way I know of to allow a system to depend on any amount of components and still have well-typed parameters.

從相關 issue #1861 以及本 issue 中提出的 Lua 範例開始。定義可變參數泛型包、映射展開和 `...` 簡寫應如何運作，然後驗證所示範的 System API 是否能夠表達具型別的元件參數和回傳值。

由索引模型根據 Issue 內容生成。