Update objc2 version (#2936)

* Upgrade to objc2 v0.4.0 and icrate v0.0.3

* Fix `touchBar` method

* Use ClassType::alloc

* Use #[method_id(...)] functionality in declare_class!

src/platform_impl/ios/mod.rs

@@ -63,7 +63,7 @@
 // window size/position.
 macro_rules! assert_main_thread {
     ($($t:tt)*) => {
-        if !::objc2::foundation::is_main_thread() {
+        if !::icrate::Foundation::is_main_thread() {
             panic!($($t)*);
         }
     };