vulkan: make Texture::uploadByteData async

Before this commit we would greedily wait for the upload to be complete
before exiting the function. This is of course not correct, since
we might be changing data that is still being used in a render in
flight. Of course we also need to cleanup the resources asynchronously
after the frame has been rendered fully.

src/modules/graphics/vulkan/Texture.h

@@ -37,7 +37,6 @@ namespace love {
 
 			private:
 				void transitionImageLayout(VkImage, VkImageLayout oldLayout, VkImageLayout newLayout);
-				void copyBufferToImage(VkBuffer, VkImage, const Rect&);
 				void createTextureImageView();
 				void createTextureSampler();
 				void clear(bool white);