make sure windows are dropped on main thread (#13686)

# Objective

- On macOS, closing a window by respawning its entity freezes

## Solution

- `WindowWrapper` is keeping an `Arc` of the window, to be able to
access it from the rendering thread. Winit windows are closed when they
are dropped. This need to happen on the main thread on macOS
- Dropping it as soon as the window is closed means the last remaining
`Arc` will be in the rendering thread
- This PR keeps the `Arc` for one frame in the rendering thread before
actually dropping it

crates/bevy_winit/src/system.rs

@@ -4,12 +4,12 @@ use bevy_ecs::{
     prelude::{Changed, Component},
     query::QueryFilter,
     removal_detection::RemovedComponents,
-    system::{NonSendMut, Query, SystemParamItem},
+    system::{Local, NonSendMut, Query, SystemParamItem},
 };
 use bevy_utils::tracing::{error, info, warn};
 use bevy_window::{
     ClosingWindow, RawHandleWrapper, Window, WindowClosed, WindowClosing, WindowCreated,
-    WindowMode, WindowResized,
+    WindowMode, WindowResized, WindowWrapper,
 };
 
 use winit::dpi::{LogicalPosition, LogicalSize, PhysicalPosition, PhysicalSize};
@@ -123,7 +123,10 @@ pub(crate) fn despawn_windows(
     mut closing_events: EventWriter<WindowClosing>,
     mut closed_events: EventWriter<WindowClosed>,
     mut winit_windows: NonSendMut<WinitWindows>,
+    mut windows_to_drop: Local<Vec<WindowWrapper<winit::window::Window>>>,
 ) {
+    // Drop all the windows that are waiting to be closed
+    windows_to_drop.clear();
     for window in closing.iter() {
         closing_events.send(WindowClosing { window });
     }
@@ -133,7 +136,13 @@ pub(crate) fn despawn_windows(
         // rather than having the component added
         // and removed in the same frame.
         if !window_entities.contains(window) {
-            winit_windows.remove_window(window);
+            if let Some(window) = winit_windows.remove_window(window) {
+                // Keeping WindowWrapper that are dropped for one frame
+                // Otherwise the last `Arc` of the window could be in the rendering thread, and dropped there
+                // This would hang on macOS
+                // Keeping the wrapper and dropping it next frame in this system ensure its dropped in the main thread
+                windows_to_drop.push(window);
+            }
             closed_events.send(WindowClosed { window });
         }
     }