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/menu.rs

@@ -1,11 +1,8 @@
-use icrate::AppKit::{
-    NSApplication, NSEventModifierFlagCommand, NSEventModifierFlagOption, NSEventModifierFlags,
-    NSMenu, NSMenuItem,
-};
-use icrate::Foundation::{ns_string, MainThreadMarker, NSProcessInfo, NSString};
 use objc2::rc::Id;
 use objc2::runtime::Sel;
 use objc2::sel;
+use objc2_app_kit::{NSApplication, NSEventModifierFlags, NSMenu, NSMenuItem};
+use objc2_foundation::{ns_string, MainThreadMarker, NSProcessInfo, NSString};
 
 struct KeyEquivalent<'a> {
     key: &'a NSString,
@@ -58,7 +55,10 @@ pub fn initialize(app: &NSApplication) {
         Some(sel!(hideOtherApplications:)),
         Some(KeyEquivalent {
             key: ns_string!("h"),
-            masks: Some(NSEventModifierFlagOption | NSEventModifierFlagCommand),
+            masks: Some(NSEventModifierFlags(
+                NSEventModifierFlags::NSEventModifierFlagOption.0
+                    | NSEventModifierFlags::NSEventModifierFlagCommand.0,
+            )),
         }),
     );