ios: fix timers

Fixes #4074.
Fixes #3816.

src/changelog/unreleased.md

@@ -48,3 +48,4 @@ changelog entry.
 
 - On X11, fix crash with uim.
 - On X11, fix modifiers for keys that were sent by the same X11 request.
+- On iOS, fix high CPU usage even when using `ControlFlow::Wait`.

src/platform_impl/ios/app_state.rs

@@ -375,6 +375,7 @@ impl AppState {
             (ControlFlow::Wait, ControlFlow::Wait) => {
                 let start = Instant::now();
                 self.set_state(AppStateImpl::Waiting { waiting_handler, start });
+                self.waker.stop()
             },
             (ControlFlow::WaitUntil(old_instant), ControlFlow::WaitUntil(new_instant))
                 if old_instant == new_instant =>