WindowServer: Move window minimize animation to a separate function

Move this from WSCompositor::compose() to a separate run_animations()
function to keep compose() readable. We might want to add some more
animations later.

Servers/WindowServer/WSCompositor.h

@@ -43,6 +43,7 @@ private:
     void draw_cursor();
     void draw_geometry_label();
     void draw_menubar();
+    void run_animations();
 
     unsigned m_compose_count { 0 };
     unsigned m_flush_count { 0 };