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/deferredshadows/debug.vert

@@ -0,0 +1,32 @@
+// Copyright 2020 Google LLC
+
+struct VSInput
+{
+[[vk::location(0)]] float3 Pos : POSITION0;
+[[vk::location(1)]] float2 UV : TEXCOORD0;
+};
+
+struct UBO
+{
+	float4x4 projection;
+	float4x4 modelview;
+};
+
+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.xy, InstanceIndex);
+	float4 tmpPos = float4(input.Pos, 1.0);
+	tmpPos.y += InstanceIndex;
+	tmpPos.xy *= float2(1.0/4.0, 1.0/3.0);
+	output.Pos = mul(ubo.projection, mul(ubo.modelview, tmpPos));
+	return output;
+}