Question mark optional syntax not supported in fun() declarations

还没有人认领这个 Issue。

### How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

Windows

### What is the issue affecting?

Type Checking

### Expected Behaviour

Optional value to actually be optional

### Actual Behaviour

It's not optional.
This code block should show as Human? and throw warnings for not checking nil. If I manually annotate with `---@param man Human?` this works as expected.

The class in question:
```lua
---@class Command
---@field info string What the command does.
---@field usage string? How to use the command.
---@field alias string[]? Aliases of the command.
---@field canCall (fun(player: Player): boolean)? Function which checks whether a player can call this command.
---@field call fun(player: Player, human: Human?, args: string[]) Calls the command.
---@field autoComplete fun(args: string[])? Function which manipulates arguments when pressing tab in the terminal.
---@field cooldownTime number? How many seconds a player has to wait before using the command again.
```

I have also tried with human?: Human and human?: Human? but neither way works.

### Reproduction steps

1. Create class with a field with a short form function declaration with an optional value parameter
2. Attempt to create object of class with that field,
3. Parameter correctly types, except as not optional.

### Additional Notes

_No response_

### Log File

_No response_

首先在 Visual Studio Code extension 中复现类字段示例，重点关注带有 nullable Human 参数的短格式函数声明。将其与手动添加注解的 `---@param man Human?` 情况进行比较；当参数被推断为可选参数，并且如描述所示出现 nil 检查警告时，即表示完成。

由索引模型根据 Issue 内容生成。