xdgoutput: separate logic for zero scaling positions

if a scaled monitor was directly to the left of another monitor, we'd change the size to have zero scaling without pushing other monitors out of the way, creating overlaps in xwayland.

src/protocols/XDGOutput.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "WaylandProtocol.hpp"
+#include <optional>
 
 class CMonitor;
 
@@ -8,6 +9,8 @@ struct SXDGOutput {
     CMonitor*                         monitor = nullptr;
     std::unique_ptr<CWaylandResource> resource;
 
+    std::optional<Vector2D>           overridePosition;
+
     wl_client*                        client     = nullptr;
     bool                              isXWayland = false;
 };