WindowServer+LibGUI: Allow specifying a "launch origin" for new windows

The launch_origin_rect parameter to create_window() specifies where on
screen the window was launched from. It's optional, but if you provide
it, the new window will have a short wireframe animation from the origin
to the initial window frame rect.

GUI::Window looks for the "__libgui_launch_origin_rect" environment
variable. Put your launch origin rect in there with the format
"<x>,<y>,<width>,<height>" and the first GUI::Window shown by the app
will use that as the launch origin rect.

Also it looks pretty neat, although I'm sure we can improve it. :^)

Userland/Services/WindowServer/WindowServer.ipc

@@ -44,7 +44,8 @@ endpoint WindowServer
         Optional<Gfx::IntSize> resize_aspect_ratio,
         i32 type,
         [UTF8] String title,
-        i32 parent_window_id) =|
+        i32 parent_window_id,
+        Gfx::IntRect launch_origin_rect) =|
 
     destroy_window(i32 window_id) => (Vector<i32> destroyed_window_ids)