WindowServer: Allow specifying different shadows for menus and tooltips

Also update the Redmond 2000 theme to drop shadows more Redmond-like.

Userland/Libraries/LibGfx/SystemTheme.h

@@ -145,6 +145,8 @@ enum class PathRole {
     NoRole,
     TitleButtonIcons,
     WindowShadow,
+    MenuShadow,
+    TooltipShadow,
     __Count,
 };