LibDraw: Introduce (formerly known as SharedGraphics.)

Instead of LibGUI and WindowServer building their own copies of the drawing
and graphics code, let's it in a separate LibDraw library.

This avoids building the code twice, and will encourage better separation
of concerns. :^)

Libraries/LibGUI/GSlider.cpp

@@ -1,6 +1,6 @@
 #include <LibGUI/GPainter.h>
 #include <LibGUI/GSlider.h>
-#include <SharedGraphics/StylePainter.h>
+#include <LibDraw/StylePainter.h>
 
 GSlider::GSlider(GWidget* parent)
     : GWidget(parent)