[Feature Request] Named Environment/Configuration Selection

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?

Windows

### What is the issue affecting?

Libraries

### Expected Behaviour

Not sure how best to word the title, but essentially, having different configuration names that the user can swap between would be nice. This is probably a *really* unlikely needed thing, but it's something I would need for my meta information.

### Actual Behaviour

You can't specify some kind of named configuration.

### Reproduction steps

N/A

### Additional Notes

If you see https://github.com/LuaLS/lua-language-server/discussions/1834, I want to be able to differentiate between when certain functions exist/overload. The problem is that I can't really do that as-is, that I can tell at least. One thing I tried to look into were the configuration file details, but there's not a lot of documentation.

Ideally, I would be able to let the user specify *how* one of my variables is defined, e.g. `love._console_name` in my case would be 3DS, Switch or Wii U. I could then do something like so:

```lua
---@meta

---
---Provides access to information about the user's system.
---
---
---[Open in Browser](https://love2d.org/wiki/love.system)
---
---@class love.system
love.system = {}

if love._console_name == "3DS" then
local play_coins = 0
---Set the Play Coin count. \
---This function is **ONLY** available on _Nintendo 3DS_.
---@param coins integer
function love.system.setPlayCoins(coins)
play_coins = coins
end

---Get the Play Coin count. \
---This function is **ONLY** available on _Nintendo 3DS_.
---@return integer current_coins
function love.system.getPlayCoins()
return play_coins
end
end

return love.system
```
and it would only show these as defined when on a "3DS" configuration.

The C++ Visual Studio Code extension has something similar:

### Log File

N/A

未指定實作檔案或測試。首先查看組態文件和討論 1834，以了解如何透過命名組態選取條件定義；完成的標準是使用者可以切換組態，並且只看到相符的定義。

由索引模型根據 Issue 內容生成。