Vulkan: Move thirdparty code out of drivers, style fixes

- `vk_enum_string_helper.h` is a generated file taken from the SDK
  (Vulkan-ValidationLayers).
- `vk_mem_alloc.h` is a library from GPUOpen:
  https://github.com/GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator

thirdparty/README.md

@@ -547,6 +547,11 @@ Files extracted from upstream source:
   `loader/` folder
 - `LICENSE.txt`
 
+`vk_enum_string_helper.h` is taken from the match `Vulkan-ValidationLayers` SDK
+release: https://github.com/KhronosGroup/Vulkan-Loader/tree/master/loader/generated
+
+`vk_mem_alloc.h` is taken from https://github.com/GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator
+
 
 ## wslay
 

thirdparty/vulkan/vk_mem_alloc.cpp

@@ -0,0 +1,7 @@
+#define VMA_IMPLEMENTATION
+#ifdef DEBUG_ENABLED
+#ifndef _MSC_VER
+#define _DEBUG
+#endif
+#endif
+#include "vk_mem_alloc.h"