Draft: render/vulkan: Delay shm texture updates till render

In order to optimize rendering of shm-backed buffers, we copy the buffer into a properly allocated texture. However, some clients might send rapid updates for large surfaces, or may not even be visible, making the copy wasteful.

Move the copy to the point where the texture is added to the render pass, ensuring that we only perform the copy if texture is being used and only once per render. This means that the shm optimization is effectively disabled for clients that are not visible.