Also remedies places where the video backends and core rely on things
being indirectly included.

Now we require lots of empty functions, but this removes by far more duplicated code.

It was only implemented in OpenGL, though the option was visible in both
backends, leading to memory leaks if you enabled it in DirectX.

And it wasn't particularly useful as a debug feature as it only showed
where in the EFB the copies were taken from, not what format it was, or
what the copy was used for, or what content was in the EFB at that point
in time.

Also, it stretched the copy regions relative to the window, so the
on-screen regions don't even line up with the window unless the game used
the full EFB (some pal games) and you game image stretched to the full
window.