WindowServer: Load multiple scaled versions of Bitmaps and Cursors

This enables rendering of mixed-scale screen layouts with e.g. high
resolution cursors and window button icons on high-dpi screens while
using lower resolution bitmaps on regular screens.

Userland/Services/WindowServer/CMakeLists.txt

@@ -21,6 +21,7 @@ set(SOURCES
     Menu.cpp
     MenuItem.cpp
     MenuManager.cpp
+    MultiScaleBitmaps.cpp
     Screen.cpp
     ScreenLayout.cpp
     Window.cpp