Reduce GPUDriver bitmap copy overhead

[SupinePandora43]

Use Surface instead of Bitmap in GPUDriver to support partial updates and custom surfaces.

Custom surface with mapped video driver memory can be used to further improve efficiency by being a direct source of vkCmdCopyBufferToImage/CopyTextureRegion.

Currently, in Vulkan, 2 full-size copies have to be made in {Create/Update}Texture calls: first from bitmap to driver's ram "staging" buffer, and second from this buffer to vram.
(From my understanding, vulkan can also use existing memory pointer (bitmap's locked pixels) with VK_EXT_EXTERNAL_MEMORY_HOST extension, but I haven't reached it yet).

What I propose will not only make these copies partial, but also remove 1 copy completely.