gpu-dawn: build with Wayland support by default; send CL to Dawn for runtime Wayland support

[emidoots]

Dawn must be built with Wayland support, right now defaulting to x11 only: https://github.com/hexops/mach-gpu-dawn/blob/62d45839942e624d08dfa6367e8bddeb8d52c8ed/sdk.zig#L12-L13

I proposed to the Dawn developers at Google we allow for Dawn to detect X11/Wayland at runtime, similar to how GLFW does it. They agreed, I need to send a CL for it:

Once we have this, we should be able to build Dawn with Wayland support by default and then #376 should be possible.

[emidoots]

#669 discovered we don't actually need to do much here, the little we did need to patch Ali sent for us upstream to Google: https://dawn-review.googlesource.com/c/dawn/+/116922