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
These were written against the shaders at revision eddd724e7.
There have been changes made since then, which will need to be mirrored.
See `data/hlsl/README.md` for the current status of each sample.