Better support for varargs in functions in classes declared with @field

还没有人认领这个 Issue。

I ran into a minor problem with how vararg is handled in function declarations in an field annotation when the function declaration itself later explicitly lists the arguments.

```
---@class Handler
---@field ReceiveMsg fun(self: Handler, type: number, ...: string)
local handler = {}

function handler:ReceiveMsg(arg1, arg2, arg3, arg4)
--- arg2 is inferred as string, but arg3 and arg4 are "any"
end
```

Why do I even have this mismatch between field and function declaration? The field annotation comes from a library and is an event handler -- the number of parameters depend on a lot of things, but for a given implementation you usually only care about a few that you explicitly declare.

首先，使用 @field ReceiveMsg vararg 注解和显式的方法声明复现 issue 的 Handler 示例。跟踪函数声明和参数推断期间 vararg 类型的传播。完成标准是 arg2、arg3 和 arg4 都一致地被推断为 string，而不是让后续参数保留为 any。

由索引模型根据 Issue 内容生成。