Add test cases for some simple descriptor types

[MarijnS95]

Include simple test cases to validate common HLSL types.

This adds an (optional) dependency on hassle-rs and dxcompiler.dll to compile the test shader; by default (cargo test) it is unused, and will only be (re)compiled with cargo test --features test-compile-shaders. Unfortunately cargo doesn't support optional dependencies in dev-dependencies, nor is there a dev-features section.

[Jasper-Bekkers]

I think we shouldn't have hassle as a dependency here, and instead just have raw strings with spirv that we disassemble with rspirv. That way we can keep the lib fully platform agnostic and just have CI on linux too (instead of adding windows).

[MarijnS95]

@Jasper-Bekkers There currently is "no dependency" on Hassle/dxcompiler unless --features test-compile-shaders is passed, which is not used on the CI. Seemed like a nice middle-ground to update the shader easily.

Adding Windows was merely to validate the entire thing compiles on both platforms, but this is pretty much implied as there are (obviously) no platform-specific pieces of code.