[Bug 45901] Avoid GPU synchronization due to GPU-CPU transfer (Overwatch)

https://bugs.winehq.org/show_bug.cgi?id=45901

--- Comment #7 from Józef Kucia  ---
I think that one problem with your patch is that it doesn't solve the issue
completely. It fixes the problem only when the source resource is a render
target. Otherwise, we still use the slow GetTexImage() path.

Other possible ways to fix the issue:
1) Optimize GetTexImage() in Mesa.
2) Use OpenGL resources for staging resources in wined3d. I think it could
avoid the issue completely. CopyResource() would be a normal raw blit between 2
GL textures. However, it isn't something that we should change lightly. It
needs some consideration, and I'm not sure if it's a very good idea.