MoltenVK Hooks

[MaddTheSane]

As it stands, a lot of emulators are starting to target more recent versions of OpenGL than what macOS supports (PPSSPP requires 4.3, but macOS only does up to 4.1). Also, OpenGL is not performant on Apple Silicon (It goes through a shim library to convert OpenGL calls to Metal). OpenGL is also lagging behind hardware capabilities of modern Macs, such as HDR. While some emulators do have a Metal back-end (Dolphin, PCSX2), a lot more are starting to rely on Vulkan for 3D rendering. While macOS doesn't natively support Vulkan, the MoltenVK library aims to translate Vulkan calls and shaders to Metal.

What needs to be done:

• Add an API that lets Cores request the needed data to start/set up a Vulkan context.
• Embed MoltenVK, or let the user select a MoltenVK that they have lying around.
• Discuss ABI stability between different versions of MoltenVK, and if periodically updating the MoltenVK library would cause any serious breaks.