As reported in issue PathOfBuildingCommunity#13, PoB tends to use significant CPU and GPU resources
while in the foreground. This change exposes a foreground frame rate limit that
can be configured via a CVar (vid_fgfps) that defaults to a 30 FPS limit and
allows a 5-120 FPS range. A setting of 30 feels responsive and reduces the
resource usage by a modest amount. CPU usage hovers around 4% on my 16-core
system with this change, as opposed to 6% usage with the current build.
Similarly, GPU usage hovers around 18-20% with the 30 FPS limit and around
25-28% with the current build.

There may be a better place to situate the sleep that is introduced for this,
but this seemed like a reasonable place for someone who is not very familiar
with this code.

I also removed the reference to tiff.lib in the Debug configuration since that
is unused and not a vcpkg dependency.