Support wgpu in guest code

[FredrikNoren]

Make it possible to use wgpu directly in the guest code.

So that:

• People can build their own renderers, or replace parts of our renderer
• People can run compute shaders
• People can use other crates that rely on wgpu, i.e. using egui, dioxus blitz etc.

Relevant info:

• Discussion on the wgpu crate: https://github.com/gfx-rs/wgpu/discussions/4201
• wgpu backends: https://github.com/gfx-rs/wgpu/tree/trunk/wgpu/src/backend (we'd likely have to create a new one)