Refactor macOS to use new objc2 features (#2465)

* Remove UnownedWindow::inner_rect

* Refactor custom view to use much less `unsafe`

The compiler fence is safe to get rid of now since `interpretKeyEvents` takes `&mut self`

* Refactor Window to use much less unsafe

* Refactor NSApplication usage to have much less unsafe

* Remove cocoa dependency

* Enable `deny(unsafe_op_in_unsafe_fn)` on macOS

Also re-enable clippy `let_unit_value` lint

* Remove #[macro_use] on macOS

* Refactor window delegate to use much less unsafe

src/platform_impl/macos/appkit/menu_item.rs

@@ -0,0 +1,48 @@
+use objc2::foundation::{NSObject, NSString};
+use objc2::rc::{Id, Shared};
+use objc2::runtime::Sel;
+use objc2::{extern_class, extern_methods, msg_send_id, ClassType};
+
+use super::{NSEventModifierFlags, NSMenu};
+
+extern_class!(
+    #[derive(Debug, PartialEq, Eq, Hash)]
+    pub(crate) struct NSMenuItem;
+
+    unsafe impl ClassType for NSMenuItem {
+        type Super = NSObject;
+    }
+);
+
+extern_methods!(
+    unsafe impl NSMenuItem {
+        pub fn new() -> Id<Self, Shared> {
+            unsafe { msg_send_id![Self::class(), new] }
+        }
+
+        pub fn newWithTitle(
+            title: &NSString,
+            action: Sel,
+            key_equivalent: &NSString,
+        ) -> Id<Self, Shared> {
+            unsafe {
+                msg_send_id![
+                    msg_send_id![Self::class(), alloc],
+                    initWithTitle: title,
+                    action: action,
+                    keyEquivalent: key_equivalent,
+                ]
+            }
+        }
+
+        pub fn separatorItem() -> Id<Self, Shared> {
+            unsafe { msg_send_id![Self::class(), separatorItem] }
+        }
+
+        #[sel(setKeyEquivalentModifierMask:)]
+        pub fn setKeyEquivalentModifierMask(&self, mask: NSEventModifierFlags);
+
+        #[sel(setSubmenu:)]
+        pub fn setSubmenu(&self, submenu: &NSMenu);
+    }
+);