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/multithreading/phong.frag

@@ -0,0 +1,20 @@
+// Copyright 2020 Google LLC
+
+struct VSOutput
+{
+[[vk::location(0)]] float3 Normal : NORMAL0;
+[[vk::location(1)]] float3 Color : COLOR0;
+[[vk::location(3)]] float3 ViewVec : TEXCOORD1;
+[[vk::location(4)]] float3 LightVec : TEXCOORD2;
+};
+
+float4 main(VSOutput input) : SV_TARGET
+{
+	float3 N = normalize(input.Normal);
+	float3 L = normalize(input.LightVec);
+	float3 V = normalize(input.ViewVec);
+	float3 R = reflect(-L, N);
+	float3 diffuse = max(dot(N, L), 0.0) * input.Color;
+	float3 specular = pow(max(dot(R, V), 0.0), 8.0) * float3(0.75, 0.75, 0.75);
+	return float4(diffuse + specular, 1.0);
+}

data/shaders/hlsl/multithreading/phong.vert

@@ -0,0 +1,49 @@
+// Copyright 2020 Google LLC
+
+struct VSInput
+{
+[[vk::location(0)]] float3 Pos : POSITION0;
+[[vk::location(1)]] float3 Normal : NORMAL0;
+[[vk::location(2)]] float3 Color : COLOR0;
+};
+
+struct PushConsts
+{
+	float4x4 mvp;
+	float3 color;
+};
+[[vk::push_constant]]PushConsts pushConsts;
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float3 Normal : NORMAL0;
+[[vk::location(1)]] float3 Color : COLOR0;
+[[vk::location(3)]] float3 ViewVec : TEXCOORD1;
+[[vk::location(4)]] float3 LightVec : TEXCOORD2;
+};
+
+VSOutput main(VSInput input)
+{
+	VSOutput output = (VSOutput)0;
+	output.Normal = input.Normal;
+
+	if ( (input.Color.r == 1.0) && (input.Color.g == 0.0) && (input.Color.b == 0.0))
+	{
+		output.Color = pushConsts.color;
+	}
+	else
+	{
+		output.Color = input.Color;
+	}
+
+	output.Pos = mul(pushConsts.mvp, float4(input.Pos.xyz, 1.0));
+
+    float4 pos = mul(pushConsts.mvp, float4(input.Pos, 1.0));
+    output.Normal = mul((float3x3)pushConsts.mvp, input.Normal);
+//	float3 lPos = ubo.lightPos.xyz;
+float3 lPos = float3(0.0, 0.0, 0.0);
+    output.LightVec = lPos - pos.xyz;
+    output.ViewVec = -pos.xyz;
+	return output;
+}

data/shaders/hlsl/multithreading/starsphere.frag

@@ -0,0 +1,35 @@
+// Copyright 2020 Google LLC
+
+#define HASHSCALE3 float3(443.897, 441.423, 437.195)
+#define STARFREQUENCY 0.01
+
+// Hash function by Dave Hoskins (https://www.shadertoy.com/view/4djSRW)
+float hash33(float3 p3)
+{
+	p3 = frac(p3 * HASHSCALE3);
+    p3 += dot(p3, p3.yxz+float3(19.19, 19.19, 19.19));
+    return frac((p3.x + p3.y)*p3.z + (p3.x+p3.z)*p3.y + (p3.y+p3.z)*p3.x);
+}
+
+float3 starField(float3 pos)
+{
+	float3 color = float3(0.0, 0.0, 0.0);
+    float threshhold = (1.0 - STARFREQUENCY);
+    float rnd = hash33(pos);
+    if (rnd >= threshhold)
+    {
+        float starCol = pow((rnd - threshhold) / (1.0 - threshhold), 16.0);
+		color += starCol.xxx;
+    }
+	return color;
+}
+
+float4 main([[vk::location(0)]] float3 inUVW : TEXCOORD0) : SV_TARGET
+{
+	// Fake atmosphere at the bottom
+	float3 atmosphere = clamp(float3(0.1, 0.15, 0.4) * (inUVW.y - 5.0), 0.0, 1.0);
+
+	float3 color = starField(inUVW) + atmosphere;
+
+	return float4(color, 1.0);
+}

data/shaders/hlsl/multithreading/starsphere.vert

@@ -0,0 +1,21 @@
+// Copyright 2020 Google LLC
+
+struct PushConsts
+{
+	float4x4 mvp;
+};
+[[vk::push_constant]]PushConsts pushConsts;
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float3 UVW : TEXCOORD0;
+};
+
+VSOutput main([[vk::location(0)]] float3 Pos : POSITION0)
+{
+	VSOutput output = (VSOutput)0;
+	output.UVW = Pos;
+	output.Pos = mul(pushConsts.mvp, float4(Pos.xyz, 1.0));
+	return output;
+}