Update objc2 crates (#3634)

Changes relevant to Winit:
- `icrate` has been deprecated in favour of separate crates per
  framework, in our case `objc2-foundation` and `objc2-app-kit` (and in
  the future `objc2-ui-kit` on iOS).
- Moved `MainThreadMarker::run_on_main` to free-standing function
  `run_on_main`.
- Changed how features work, this should result in less code that we
  need to compile.
- Enums are now real structs instead of type-aliases and free constants.

src/platform_impl/macos/cursor.rs

@@ -2,14 +2,14 @@ use std::ffi::c_uchar;
 use std::slice;
 use std::sync::OnceLock;
 
-use icrate::AppKit::{NSBitmapImageRep, NSCursor, NSDeviceRGBColorSpace, NSImage};
-use icrate::Foundation::{
-    ns_string, NSData, NSDictionary, NSNumber, NSObject, NSObjectProtocol, NSPoint, NSSize,
-    NSString,
-};
 use objc2::rc::Id;
 use objc2::runtime::Sel;
 use objc2::{msg_send_id, sel, ClassType};
+use objc2_app_kit::{NSBitmapImageRep, NSCursor, NSDeviceRGBColorSpace, NSImage};
+use objc2_foundation::{
+    ns_string, NSData, NSDictionary, NSNumber, NSObject, NSObjectProtocol, NSPoint, NSSize,
+    NSString,
+};
 
 use crate::cursor::CursorImage;
 use crate::cursor::OnlyCursorImageSource;
@@ -19,7 +19,7 @@ use crate::window::CursorIcon;
 pub struct CustomCursor(pub(crate) Id<NSCursor>);
 
 // SAFETY: NSCursor is immutable and thread-safe
-// TODO(madsmtm): Put this logic in icrate itself
+// TODO(madsmtm): Put this logic in objc2-app-kit itself
 unsafe impl Send for CustomCursor {}
 unsafe impl Sync for CustomCursor {}