`@overload` does not cooperate with `@class` when adding overloads to an inherited class method

Nobody has claimed this yet.

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

NeoVim

### Which OS are you using?

Linux

### What is the issue affecting?

Completion

### Expected Behaviour

Adding an overload to a function inherited from another class should result in both the parent class' overloads and the new overload being suggested as autocomplete and hover tooltip entries.

### Actual Behaviour

Adding an overload to a function inherited from another class makes that overload the only one that is recognized for the current class.

### Reproduction steps

```lua
---@meta

---@class ParentClass
ParentClass = {}

---@param arg string
---@return unknown
---@overload fun(self, arg: "bar"): boolean
function ParentClass:foo(arg) end

---@class ChildClass : ParentClass
---@field foo fun(self, arg: "baz"): number
ChildClass = {}

ChildClass:foo(--[[Should suggest both "bar" and "baz", but only suggests "baz" and "bar" raises a param-type-mismatch]])
```
Redefining the function and adding an `@overload` there yields the same result.

### Additional Notes

Having some way to mark a function redefinition as an overload (with strict checking that it does exist in the class defined as inherited from) would probably help solve this issue.

### Log File

_No response_

Start with the Lua annotation and completion behavior shown in the reproduction, focusing on how @class inheritance and @overload declarations are handled. Reproduce the case in NeoVim and verify that completion and hover show both the inherited "bar" overload and the child "baz" overload without a parameter-type mismatch.

Written by the indexing model from the issue text.