Change run_app(app: &mut A) to run_app(app: A) (#3721)

This allows the user more control over how they pass their application state
to Winit, and will hopefully allow `Drop` implementations on the application
handler to work in the future on all platforms.

examples/child_window.rs

@@ -86,8 +86,7 @@ fn main() -> Result<(), impl std::error::Error> {
     }
 
     let event_loop = EventLoop::new().unwrap();
-    let mut app = Application::default();
-    event_loop.run_app(&mut app)
+    event_loop.run_app(Application::default())
 }
 
 #[cfg(all(feature = "rwh_06", not(any(x11_platform, macos_platform, windows_platform))))]

examples/control_flow.rs

@@ -43,8 +43,7 @@ fn main() -> Result<(), impl std::error::Error> {
 
     let event_loop = EventLoop::new().unwrap();
 
-    let mut app = ControlFlowDemo::default();
-    event_loop.run_app(&mut app)
+    event_loop.run_app(ControlFlowDemo::default())
 }
 
 #[derive(Default)]

examples/window.rs

@@ -57,9 +57,8 @@ fn main() -> Result<(), Box<dyn Error>> {
         }
     });
 
-    let mut state = Application::new(&event_loop);
-
-    event_loop.run_app(&mut state).map_err(Into::into)
+    let app = Application::new(&event_loop);
+    Ok(event_loop.run_app(app)?)
 }
 
 /// Application state and event handling.

examples/x11_embed.rs

@@ -58,8 +58,7 @@ fn main() -> Result<(), Box<dyn Error>> {
     tracing_subscriber::fmt::init();
     let event_loop = EventLoop::new()?;
 
-    let mut app = XEmbedDemo { parent_window_id, window: None };
-    event_loop.run_app(&mut app).map_err(Into::into)
+    Ok(event_loop.run_app(XEmbedDemo { parent_window_id, window: None })?)
 }
 
 #[cfg(not(x11_platform))]