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/hlsl/texturearray/instancing.frag

@@ -0,0 +1,9 @@
+// Copyright 2020 Google LLC
+
+Texture2DArray textureArray : register(t1);
+SamplerState samplerArray : register(s1);
+
+float4 main([[vk::location(0)]] float3 inUV : TEXCOORD0) : SV_TARGET
+{
+	return textureArray.Sample(samplerArray, inUV);
+}

data/shaders/hlsl/texturearray/instancing.vert

@@ -0,0 +1,37 @@
+// Copyright 2020 Google LLC
+
+struct VSInput
+{
+[[vk::location(0)]] float3 Pos : POSITION0;
+[[vk::location(1)]] float2 UV : TEXCOORD0;
+};
+
+struct Instance
+{
+	float4x4 model;
+	float4 arrayIndex;
+};
+
+struct UBO
+{
+	float4x4 projection;
+	float4x4 view;
+	Instance instance[8];
+};
+
+cbuffer ubo : register(b0) { UBO ubo; }
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float3 UV : TEXCOORD0;
+};
+
+VSOutput main(VSInput input, uint InstanceIndex : SV_InstanceID)
+{
+	VSOutput output = (VSOutput)0;
+	output.UV = float3(input.UV, ubo.instance[InstanceIndex].arrayIndex.x);
+	float4x4 modelView = mul(ubo.view, ubo.instance[InstanceIndex].model);
+	output.Pos = mul(ubo.projection, mul(modelView, float4(input.Pos, 1.0)));
+	return output;
+}