Class generics produce unusable and wrong union types

還沒有人認領這個 Issue。

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

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

MacOS, Windows

### What is the issue affecting?

Completion

### Expected Behaviour

Methods `Peek,Push,Pop` have proper type hints

### Actual Behaviour

While types of `a, b, c` are correct the
type hints of methods are unusable with unnecessary union types.

**If `Push` is removed from superclass, then type hints go to normal without unions but still with `` in many places**

```lua
local _lua_setmetatable = setmetatable

Stack = {}

--- @generic T
--- @class Stack : {
--- Pop: (fun(self: Stack): T),
--- Peek: (fun(self: Stack): T),
--- Push: (fun(self: Stack, value: T): Stack),
--- }
--- @field protected _stack any[]
--- @field protected _count integer
Stack.__index = {}

--- Creates a new, empty stack.
--- @generic T
--- @return Stack
function Stack.New()
local this = {
_stack = {},
_count = 0,
}

return _lua_setmetatable(this, Stack)
end

local st = Stack.New() --[[@as Stack<{ num: integer }>]]

local a = st:Peek()
local b = st:Pop()
local c = st:Push({})
```

### Reproduction steps

Analyze specified code in VSCode with luals installed

### Additional Notes

_No response_

### Log File

_No response_

透過在安裝了 lua-language-server 的 VS Code 中分析 Lua 程式碼片段來重現問題，重點關注 Stack.New 以及 Peek、Pop 和 Push 方法的補全提示。將 a、b 和 c 的推斷型別與預期的非聯集型別方法提示進行比較；當這些方法不再顯示無法使用或不必要的聯集型別，也不再顯示多餘的泛型佔位符時，即表示完成。

由索引模型根據 Issue 內容生成。