WindowLevel::AlwaysOnTop not working

## Bevy version and features

- version = "0.18.1"
- default-features = false
- features = ["default_app", "default_platform"]

## \[Optional\] Relevant system information

- Linux Mint 22.3
- X11

## What you did

```
app.add_plugins(DefaultPlugins.set(WindowPlugin {
primary_window: Some(Window {
title: "Buggy Critters".to_string(),
resizable: false,
mode: bevy::window::WindowMode::Windowed,
window_level: bevy::window::WindowLevel::AlwaysOnTop,
focused: true,
decorations: false,
position: WindowPosition::At(IVec2::new(0, 0)),
..Default::default()
}),
..Default::default()
}));
```

## What went wrong

It seems to work for like 5 seconds but then after that at it stops and windows can cover it.

## Additional information

I tried to do it directly with Winit, and it works fine, so I don't think its the operating system. I know there is another issue about the same problem, but it a previous version and my cargo looks different so I wanted to still ask.

First reproduce the example with Bevy 0.18.1 on Linux Mint 22.3 using X11, then inspect the WindowPlugin and WindowLevel::AlwaysOnTop handling and compare it with the reported direct Winit behavior. Done means the configured window remains above other windows beyond the initial five seconds.

Written by the indexing model from the issue text.