metal: send non-desktop outputs to the frontend

src/it/test_backend.rs

@@ -106,6 +106,7 @@ impl TestBackend {
             initial_mode: mode,
             width_mm: 80,
             height_mm: 60,
+            non_desktop: false,
         };
         Self {
             state: state.clone(),

src/it/tests/t0034_workspace_restoration.rs

@@ -42,6 +42,7 @@ async fn test(run: Rc<TestRun>) -> TestResult {
         },
         width_mm: 0,
         height_mm: 0,
+        non_desktop: false,
     };
     run.backend
         .state