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/closesthit.rchit

@@ -1,12 +0,0 @@
-#version 460
-#extension GL_NV_ray_tracing : require
-#extension GL_EXT_nonuniform_qualifier : enable
-
-layout(location = 0) rayPayloadInNV vec3 hitValue;
-hitAttributeNV vec3 attribs;
-
-void main()
-{
-  const vec3 barycentricCoords = vec3(1.0f - attribs.x - attribs.y, attribs.x, attribs.y);
-  hitValue = barycentricCoords;
-}