Sort physical devices on macOS platforms

[charles-lunarg]

These platforms do not have a ton of drivers available for them, but they do have a mix of physical (MoltenVK) and CPU (swiftshader) implementations. While most apps are good about choosing the GPU they want, the loader currently doesn't specify the ordering of drivers on macOS. Since there is ongoing work to rectify that for Linux, a similar albeit smaller in scope change should be added for macOS.

My proposed ordering is to ensure that CPU implementations appear after the hardware implementations. This prevents using the CPU for rendering when the app didn't intend to do so.