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_reflections/miss.rmiss

@@ -1,25 +0,0 @@
-#version 460
-#extension GL_NV_ray_tracing : require
-
-struct RayPayload {
-	vec3 color;
-	float distance;
-	vec3 normal;
-	float reflector;
-};
-
-layout(location = 0) rayPayloadInNV RayPayload rayPayload;
-
-void main()
-{
-	// View-independent background gradient to simulate a basic sky background
-	const vec3 gradientStart = vec3(0.5, 0.6, 1.0);
-	const vec3 gradientEnd = vec3(1.0);
-	vec3 unitDir = normalize(gl_WorldRayDirectionNV);
-	float t = 0.5 * (unitDir.y + 1.0);
-	rayPayload.color = (1.0-t) * gradientStart + t * gradientEnd;
-
-	rayPayload.distance = -1.0f;
-	rayPayload.normal = vec3(0.0f);
-	rayPayload.reflector = 0.0f;
-}