Use Shady for HSLS and Metal Shaders.

[treeform]

• add one shared Shady-authored Silky shader for the OpenGL, DirectX, and Vulkan drawers

• move viewport and atlas transforms into shader uniforms instead of backend-specific shader text

• preserve the current tooltip mask path by carrying maskUv through the shared shader

• add source-shader development mode for DirectX and Vulkan that writes generated source files and refreshes committed bytecode blobs

• add shadyBinaryShaders mode for DirectX .cso and Vulkan .spv blobs when source shader generation/compilation should be skipped

• add shader codegen coverage and a DirectX runtime smoke test for generated HLSL pipeline creation

• depends on Add HLSL and Metal Shader support. shady#33 at f9ab26d946c32cd9da7c04394a1353a375a9dba5 for the Vulkan GLSL target, HLSL resource binding, and binary shader utility support