Class Inheritance Triggers Typing Issues

Nobody has claimed this yet.

### 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, Diagnostics/Syntax Checking

### Expected Behaviour

To put it in plain terms, this is for a system of UserControls for a settings-panel system. There is a single Superclass, called "MCT.Option", which houses all of the unified behavior of all the UserControls. Then there are subclasses, for each type of UserControl - checkbox, dropdown, etc.

There's an abstracted method on the UserControl "holders", `holder:get_option_by_key("user_control_key')` that I have annotated as returning an MCT.Option. In reality, that superclass is never actually returned in practice - it's purely abstracted, and any option is one of the several subclasses.

So when I call:
```
---@type MCT.Option.Checkbox
local option = holder:get_option_by_key("i_know_this_is_a_checkbox")
```
I'm expecting to very easily call a conversion from superclass -> subclass.

I have all that (I think) I need to tell the debugger that it's a subclass: initial definition of the subclass is `---@class MCT.Option.Checkbox : MCT.Option, Class` to tell it its parents, and it reads from the higher methods and properties completely fine.

But when I call ---@type like that, the debugger doesn't let me simply convert from one to another.

I can of course use `---@cast option MCT.Option.Checkbox` after the variable is defined, but that's a bit clunkier in my opinion than having the type defined above the variable, and it ends up requiring me to reference the variable in the annotation, so it takes a bit longer to write up (and I have a lot of these!)

### Actual Behaviour


### Reproduction steps

1. Create a superclass:
```
---@class MySuperclass
local o = {}
```
2. Create a subclass:
```
---@class MySubclass : MySuperclass
local o = {}
```
3. Create a function that returns MySuperclass
4. Try to direct the type that returns from that function into MySublass

### Additional Notes

Thank you for all the hard work you've done over the years - I've been using this extension for a very very long time and it's truly a lifesaver.

### Log File

[file_s%3A_modding_warhammer_3_groovy_mct.log](https://github.com/LuaLS/lua-language-server/files/10698513/file_s.3A_modding_warhammer_3_groovy_mct.log)

Start by reproducing the superclass and subclass examples in the issue through the Visual Studio Code extension on Windows, focusing on the type-checking diagnostic for assigning a MySuperclass result to MySubclass. Trace the type-checking behavior involved in class inheritance and confirm that the assignment is accepted without requiring @cast when the fix is complete.

Written by the indexing model from the issue text.