0.16 Regression fix: re-expose the display handle via a wrapper resource (#18644)

# Objective

- In the latest released version (15.3) I am able to obtain this
information by getting the actual `EventLoop` via `non_send_resource`.
Now that this object has (probably rightfully so) been replaced by the
`EventLoopProxy`, I can no longer maintain my custom render backend:
https://github.com/HugoPeters1024/bevy_vulkan. I also need the display
handle for a custom winit integration, for which I've made patches to
bevy before: XREF: https://github.com/bevyengine/bevy/pull/15884


## Solution

- Luckily, all that is required is exposing the `OwnedDisplayHandle` in
its own wrapper resource.

## Testing

- Aforementioned custom rendering backend works on this commit.

---------

Co-authored-by: HugoPeters1024 <hugopeters1024@gmail.com>

crates/bevy_winit/src/lib.rs

@@ -127,6 +127,7 @@ impl<T: Event> Plugin for WinitPlugin<T> {
         app.init_non_send_resource::<WinitWindows>()
             .init_resource::<WinitMonitors>()
             .init_resource::<WinitSettings>()
+            .insert_resource(DisplayHandleWrapper(event_loop.owned_display_handle()))
             .add_event::<RawWinitWindowEvent>()
             .set_runner(|app| winit_runner(app, event_loop))
             .add_systems(
@@ -176,6 +177,15 @@ pub struct RawWinitWindowEvent {
 #[derive(Resource, Deref)]
 pub struct EventLoopProxyWrapper<T: 'static>(EventLoopProxy<T>);
 
+/// A wrapper around [`winit::event_loop::OwnedDisplayHandle`]
+///
+/// The `DisplayHandleWrapper` can be used to build integrations that rely on direct
+/// access to the display handle
+///
+/// Use `Res<DisplayHandleWrapper>` to receive this resource.
+#[derive(Resource, Deref)]
+pub struct DisplayHandleWrapper(pub winit::event_loop::OwnedDisplayHandle);
+
 trait AppSendEvent {
     fn send(&mut self, event: impl Into<WindowEvent>);
 }