renderer_vulkan: Initialize surface in separate file

Move surface initialization code to a separate file. It's unlikely to
use this code outside of Vulkan, but keeping platform-specific code
(Win32, Xlib, Wayland) in its own translation unit keeps things cleaner.

src/video_core/CMakeLists.txt

@@ -264,6 +264,8 @@ add_library(video_core STATIC
     vulkan_common/vulkan_instance.h
     vulkan_common/vulkan_library.cpp
     vulkan_common/vulkan_library.h
+    vulkan_common/vulkan_surface.cpp
+    vulkan_common/vulkan_surface.h
     vulkan_common/vulkan_wrapper.cpp
     vulkan_common/vulkan_wrapper.h
 )