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/hlsl/textoverlay/text.frag

@@ -1,10 +0,0 @@
-// Copyright 2020 Google LLC
-
-Texture2D textureFont : register(t0);
-SamplerState samplerFont : register(s0);
-
-float4 main([[vk::location(0)]] float2 inUV : TEXCOORD0) : SV_TARGET
-{
-	float color = textureFont.Sample(samplerFont, inUV).r;
-	return color.xxxx;
-}