MoltenVK Updated For Vulkan 1.2 Support On Apple macOS/iOS

MoltenVK 1.2 was tagged today and with this version there is now support for Vulkan 1.2. This MoltenVK 1.2 release is built against the Vulkan SDK 1.3.231 and also exposes SPIR-V 1.4 support, KHR_shader_float_controls, improves Vulkan semaphore functionality, memory leaks have been addressed, crash fixes, and a variety of other improvements for mapping Vulkan to Metal.