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/base/uioverlay.vert

@@ -0,0 +1,33 @@
+// Copyright 2020 Google LLC
+
+struct VSInput
+{
+	[[vk::location(0)]]float2 Pos : POSITION0;
+	[[vk::location(1)]]float2 UV : TEXCOORD0;
+	[[vk::location(2)]]float4 Color : COLOR0;
+};
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+	[[vk::location(0)]]float2 UV : TEXCOORD0;
+	[[vk::location(1)]]float4 Color : COLOR0;
+};
+
+struct PushConstants
+{
+	float2 scale;
+	float2 translate;
+};
+
+[[vk::push_constant]]
+PushConstants pushConstants;
+
+VSOutput main(VSInput input)
+{
+	VSOutput output = (VSOutput)0;
+	output.Pos = float4(input.Pos * pushConstants.scale + pushConstants.translate, 0.0, 1.0);
+	output.UV = input.UV;
+	output.Color = input.Color;
+	return output;
+}