Move shaders into glsl and hlsl directories

Move `data/shaders` to `data/shaders/glsl`
Move `data/hlsl` to `data/shaders/hlsl`

Fix up shader paths in the cpp files to point to the new glsl location.

`data/shaders/hlsl/compile.py` still overwrites the glsl .spv files (for
now).

Issue: #723

data/shaders/nv_ray_tracing_basic/miss.rmiss

@@ -1,9 +0,0 @@
-#version 460
-#extension GL_NV_ray_tracing : require
-
-layout(location = 0) rayPayloadInNV vec3 hitValue;
-
-void main()
-{
-    hitValue = vec3(0.0, 0.0, 0.2);
-}