Proposal: Add @constructor Tag for Class Constructors in Lua LSP

This Lua LSP could benefit from a new @constructor tag, which would be used when defining classes, especially with libraries. Currently, we have to do something like this:

---@class myCls
---@overload fun(a: integer, b: integer): myCls
local myCls = class "myCls"

---@param a integer
---@param b integer
function myCls:__init(a, b)
     self.a = a
     self.b = b
end
local instance = myCls(10, 20)
print(instance)

As you can see, we need to create an overload for the variable, which makes the typing process quite repetitive. To address this, we could introduce a new @constructor tag that would automatically handle this:

---@class myCls
local myCls = class "myCls" -- No need for an overload anymore.

-- Defining this method as the constructor:
---@constructor
---@param a integer
---@param b integer
function myCls:__init(a, b)
     self.a = a
     self.b = b
end
local instance = myCls(10, 20) -- Type checking would work correctly and show the constructor parameters.
print(instance)

This approach would make the code cleaner and more intuitive, reducing the need for repetitive annotations and improving the overall developer experience.

首先根据此 issue 中的示例检查现有的 @class 和 @overload 行为；未指定文件、测试或入口点。完成的标准应是：使用 @constructor 标记 init 后，能够为 myCls(10, 20) 这样的调用提供构造函数参数，而无需单独的 overload。