Reduce amount of unsafe on iOS (#2579)

* Use objc2::foundation CG types

* Add safe abstraction over UIApplication

* Add safe abstraction over UIDevice

* Add safe abstraction over UIScreen

* Add safe abstraction over UIWindow

* Add safe abstraction over UIViewController

* Add safe abstraction over UIView

* Appease clippy

src/platform_impl/ios/uikit/application.rs

@@ -0,0 +1,30 @@
+use objc2::foundation::{CGRect, MainThreadMarker, NSArray, NSObject};
+use objc2::rc::{Id, Shared};
+use objc2::{extern_class, extern_methods, msg_send_id, ClassType};
+
+use super::{UIResponder, UIWindow};
+
+extern_class!(
+    #[derive(Debug, PartialEq, Eq, Hash)]
+    pub(crate) struct UIApplication;
+
+    unsafe impl ClassType for UIApplication {
+        #[inherits(NSObject)]
+        type Super = UIResponder;
+    }
+);
+
+extern_methods!(
+    unsafe impl UIApplication {
+        pub fn shared(_mtm: MainThreadMarker) -> Option<Id<Self, Shared>> {
+            unsafe { msg_send_id![Self::class(), sharedApplication] }
+        }
+
+        pub fn windows(&self) -> Id<NSArray<UIWindow, Shared>, Shared> {
+            unsafe { msg_send_id![self, windows] }
+        }
+
+        #[sel(statusBarFrame)]
+        pub fn statusBarFrame(&self) -> CGRect;
+    }
+);