gpui: Fix hide, activate method on Windows to hide/show application (#18164)

Release Notes:

- N/A

Continue #18161 to fix `cx.hide`, `cx.activate` method on Windows to
hide/show application.

## After


https://github.com/user-attachments/assets/fe0070f9-7844-4c2a-b859-3e22ee4b8d22

---------

Co-authored-by: Mikayla Maki <mikayla@zed.dev>

crates/gpui/examples/window.rs

@@ -150,6 +150,18 @@ impl Render for WindowDemo {
                 )
                 .unwrap();
             }))
+            .child(button("Hide Application", |cx| {
+                cx.hide();
+
+                // Restore the application after 3 seconds
+                cx.spawn(|mut cx| async move {
+                    Timer::after(std::time::Duration::from_secs(3)).await;
+                    cx.update(|cx| {
+                        cx.activate(false);
+                    })
+                })
+                .detach();
+            }))
     }
 }