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/deferredmultisampling/debug.vert

@@ -0,0 +1,23 @@
+// Copyright 2020 Google LLC
+
+struct UBO
+{
+	float4x4 projection;
+	float4x4 model;
+};
+
+cbuffer ubo : register(b0) { UBO ubo; }
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float3 UV : TEXCOORD0;
+};
+
+VSOutput main(uint VertexIndex : SV_VertexID)
+{
+	VSOutput output = (VSOutput)0;
+	output.UV = float3((VertexIndex << 1) & 2, VertexIndex & 2, 0.0);
+	output.Pos = float4(output.UV.xy * 2.0f - 1.0f, 0.0f, 1.0f);
+	return output;
+}