[Feature Request] Required nullable arguments

還沒有人認領這個 Issue。

When calling Java methods from Kahlua, the number of arguments is used to determine the appropriate implementation to call. Because of this, arguments that can be `nil` are required in the function call for appropriate resolution. This is usually not a concern in Lua, but it could be.

In this example, both `f()` and `f(nil)` are appropriate, since the value of `x` defaults to `nil`.
```
---@param x integer?
local function f(x) end
```

In this example, however, the behaviors of `t.f()` and `t.f(nil)` are *not* equivalent.
(Admittedly, this is a contrived example. Nonetheless, it shows that this would not only be useful for strange cases like Kahlua's implementation.)
```
---@class Example
---@field f fun(x: integer?)
t = {
f = function(...)
assert(select('#', ...) == 1)
end
}
```

---

I don't feel strongly about the annotation that would be used to specify this, but `!` comes to mind:
```
---@class Example
---@field f fun(x: integer?!)
t = {
f = function(...)
assert(select('#', ...) == 1)
end
}
```

The `?!`/`!?` pair may be redundant, since non-nil argument types are always required. It would also be feasible to represent required but nil-able arguments with `!` alone.

未指定任何 repository 檔案或測試。首先找出與 Lua 函式和 Java/Kahlua 呼叫相關的註解處理路徑以及參數數量解析路徑。比較提議的 `?!`、`!?` 和 `!` 形式，接著定義對省略參數與明確 `nil` 參數的涵蓋範圍，並在實作前確認預期的語法。

由索引模型根據 Issue 內容生成。