Decide & implement a design for ray tracing pipelines

[Vecvec]

Is your feature request related to a problem? Please describe.
Currently naga only supports ray queries, however for some (very specific) use-cases ray tracing pipelines could be useful. E.g user defined custom intersection easier without having to change other parts of the shader.

Describe the solution you'd like
To support raytracing pipeline

Describe alternatives you've considered
Not supporting it, it's not really necessary.

Additional context
We also need to decide on some API for raytracing pipelines

[Vecvec]

Just want to note some of my previous work in naga, so here is an old WIP raytracing pipeline suggestion (or at least the naga side of it):

• use @intersection for intersection shaders, @ray_any for any-hit shaders, @ray_closest for closest hit shaders, @ray_miss for ray-miss shaders, and @ray_gen for ray generation shaders (callable shaders were not implemented as they seemed like they were not required.
• intersection shaders means intersection shader, closest hit shader any hit shader.
• use @builtin(payload) with a pointer in the ray tracing address space (no requirement on struct, maybe should be same as vertex -> fragment?) allowed in all but ray_gen shaders.
• use @builtin({world/object}_ray_{origin/direction}) to get the origin/direction in the world/object space allowed in intersection shaders.
• use @builtin(ray_{origin/direction}) in the miss shader to get origin/direction in the shader.
• use @builtin(ray_t) in the intersection shaders to get the t on the ray of the hit.
• many more builtins that I need to clarify what they do.
• functions:

// begins a trace ray, allowed in generation and closest hit shaders
fn traceRay(ray_struct: ptr<{function/ray_tracing}, ray_query>, acceleration_structure: acceleration_structure, ray_desc: RayDesc);

// the t of the intersection, the type, and an extra u32 to communicate (I've forgotten exactly what this does right now) returns whether the hit was accepted.
fn ReportIntersection(t: f32, ty:u32, intersection:u32) -> bool;

edit: just want to note that it mostly worked but need some hardening ect.