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/hlsl/displacement/base.frag

@@ -1,26 +0,0 @@
-// Copyright 2020 Google LLC
-
-Texture2D textureColorMap : register(t2);
-SamplerState samplerColorMap : register(s2);
-
-struct DSOutput
-{
-[[vk::location(0)]] float3 Normal : NORMAL0;
-[[vk::location(1)]] float2 UV : TEXCOORD0;
-[[vk::location(2)]] float3 EyePos : POSITION0;
-[[vk::location(3)]] float3 LightVec : TEXCOORD2;
-};
-
-float4 main(DSOutput input) : SV_TARGET
-{
-	float3 N = normalize(input.Normal);
-	float3 L = normalize(float3(1.0, 1.0, 1.0));
-
-	float3 Eye = normalize(-input.EyePos);
-	float3 Reflected = normalize(reflect(-input.LightVec, input.Normal));
-
-	float4 IAmbient = float4(0.0, 0.0, 0.0, 1.0);
-	float4 IDiffuse = float4(1.0, 1.0, 1.0, 1.0) * max(dot(input.Normal, input.LightVec), 0.0);
-
-	return float4((IAmbient + IDiffuse) * float4(textureColorMap.Sample(samplerColorMap, input.UV).rgb, 1.0));
-}