Paths to vulkan libraries, paths and related components were
hardcoded in the platform cmake file. This patch separates
this by using adding CMake modules for Vulkan and ShaderC.
This change has only been applied to the macOs configuration as
that is currently our main platform for development. Other platforms
will be added during the development of the Vulkan back-end.
Vulkan doesn't have a memory allocator builtin. The application should
provide the memory allocator at runtime. Vulkan Memory Allocator is a
widely used implementation.
Vulkan Memory Allocator is a header only implementation, but the using
application should compile a part in a CPP compile unit. The file
`vk_mem_alloc_impl.cc` and `extern_vulkan_memory_allocator` library
is therefore introduced.
Reviewed By: fclem
Differential Revision: https://developer.blender.org/D16572
