vk_instance: Make DynamicLoader static

* That way we don't construct/destroy it all the time

src/video_core/renderer_vulkan/vk_instance.cpp

@@ -13,6 +13,8 @@
 
 namespace Vulkan {
 
+vk::DynamicLoader Instance::dl;
+
 vk::Format ToVkFormat(VideoCore::PixelFormat format) {
     switch (format) {
     case VideoCore::PixelFormat::RGBA8:

src/video_core/renderer_vulkan/vk_instance.h

@@ -144,7 +144,7 @@ private:
     void CreateAllocator();
 
 private:
-    vk::DynamicLoader dl;
+    static vk::DynamicLoader dl;
     vk::Device device;
     vk::PhysicalDevice physical_device;
     vk::Instance instance;