Add debugPrintf to wgsl

[exrook]

Moved to gfx-rs/wgpu#4297

We can have printf in shaders :)

Supports wgsl-in, spv-in, spv-out, hlsl-out, glsl-out

Supporting glsl-in would need changes upstream in https://github.com/Kangz/glslpp-rs/ to parse the format strings.

msl has no support for this sort of feature as far as I can tell.

for more info see: https://github.com/KhronosGroup/Vulkan-ValidationLayers/blob/main/docs/debug_printf.md

cc: gfx-rs/wgpu#4410

[exrook]

I'm disabling the test for hlsl-out since dxc doesn't support printf when outputting dxil. I'll keep the hlsl-out feature in since it still does work with fxc, and with dxc when targeting spirv.

[jimblandy]

If I understand our plan correctly, I think this needs a bit in valid::Capabilities as well.

[jimblandy]

Tragically, Mesa doesn't support SPV_KHR_non_semantic_info, so I can't try this out.

[exrook]

Tragically, Mesa doesn't support SPV_KHR_non_semantic_info, so I can't try this out.

It's working on my machine with mesa 23.2.1 ;) , although I had to explicitly enable printf in the validation layer using the vulkan configurator in order to see output. I think it's possible to programmatically enable as well but I haven't looked into that yet.

I also have a local patch to wgpu that enables VK_KHR_shader_non_semantic_info but that doesn't seem to have any effect, my shader compiles & runs regardless of whether it's enabled or not.

If I understand our plan correctly, I think this needs a bit in valid::Capabilities as well.

I'll try to figure this out, currently no other Statements interact with Capabilities so it's not immediately obvious to me where the check should end up.