Minimal reproduction of a potential wgpu-rs bug

This application is simply supposed to draw a grid of lines on the screen. On some Windows 10 machines using the DirectX12 backend, when the iced-wgpu backend is initialized before my custom backend the grid disappears. This does not happen in DirectX11, or Vulkan on Linux. On some machines the DirectX12/iced-wgpu combo does work; luckily it seems to be reproducible in a Windows 10 VM.

Steps to reproduce

• Create a fresh Windows 10 x64 VM in VirtualBox (may not be necessary if your host machine exhibits the described behaviour, as some have)
• The VC++ redist might be needed; you can get it here
• Compile the project (transferring to the VM if necessary), and run it with the given arguments: dx12 iced. If the bug occurs, the window should remain blank. Passing just iced or just dx12 should both display the grid, as in the former case the app defaults to DirectX11 and in the latter the iced backend is not initialized.