CI: Use libMainThreadChecker to test if all functions run on the correct thread

[pentamassiv]

Xcode provides a tool called the “Main Thread Checker” which verifies that UI APIs are being used from the correct thread. More information can be found here: https://developer.apple.com/documentation/xcode/diagnosing-memory-thread-and-crash-issues-early#Detect-improper-UI-updates-on-background-threads

Tauri crashes when enigo is not used on the main thread. With this tool, we can make sure everything runs on the correct thread

[pentamassiv]

I think there should be warnings. I thought that the tests run in individual threads. It might be a good idea to add a Tauri example and make sure it doesn't crash even if enigo is used in a new thread (see tauri-apps/tauri#6421 (comment))

[pentamassiv]

I just cannot get it to work. The MainThreadChecker runs and throws an error as expected if the integration_browser test gets replaced with (source):

//! Run [NSView new] on a separate thread, which should get caught by the
//! main thread checker.
use objc2::rc::Id;
use objc2::runtime::AnyObject;
use objc2::{class, msg_send_id};

#[link(name = "AppKit", kind = "framework")]
unsafe extern "C" {}

#[test]
fn integration_browser_events() {
    std::thread::scope(|s| {
        s.spawn(|| {
            // Note: Usually you'd use `icrate::NSView::new`, this is to
            // avoid the heavy dependency.
            let _: Id<AnyObject> = unsafe { msg_send_id![class!(NSView), new] };
        });
    });
}

But it does not fail when I try to run enigo functions in another thread. I would expect it to fail then too