fix: make sure that cargo test can be killed with ctrl+c

I am not sure why we were catching ctrl+c in the first place. This was
introduced in near#4229 I think. But messing up with signal handlers in
tests doesn't feel right and, indeed, prevents tests from being killed.

Test Plan
---------

Manual testing: running `cargo t -p integration-tests` and then killing
it in the middle with ctrl+c leaves the test running in the background
before this PR, and properly kills the process after.

test-utils/actix-test-utils/src/lib.rs

@@ -1,10 +1,5 @@
-use actix_rt::signal;
-use futures::{future, select, task::Poll, FutureExt};
 use once_cell::sync::Lazy;
-use std::sync::{
-    atomic::{AtomicBool, Ordering},
-    Mutex,
-};
+use std::sync::Mutex;
 
 pub struct ShutdownableThread {
     pub join: Option<std::thread::JoinHandle<()>>,
@@ -40,32 +35,11 @@ impl Drop for ShutdownableThread {
     }
 }
 
-static CAUGHT_SIGINT: AtomicBool = AtomicBool::new(false);
-
-macro_rules! handle_interrupt {
-    ($future:expr) => {
-        async move {
-            assert!(!CAUGHT_SIGINT.load(Ordering::SeqCst), "SIGINT received");
-            select! {
-                _ = {
-                    future::poll_fn(|_| {
-                        if CAUGHT_SIGINT.load(Ordering::SeqCst) {
-                            return Poll::Ready(());
-                        }
-                        Poll::Pending
-                    })
-                }.fuse() => panic!("SIGINT received"),
-                output = $future.fuse() => output,
-            }
-        }
-    };
-}
-
 #[inline]
 pub fn spawn_interruptible<F: std::future::Future + 'static>(
     f: F,
 ) -> actix_rt::task::JoinHandle<F::Output> {
-    actix_rt::spawn(handle_interrupt!(f))
+    actix_rt::spawn(f)
 }
 
 // Number of actix instances that are currently running.
@@ -80,38 +54,20 @@ pub fn setup_actix() -> actix_rt::SystemRunner {
         let default_hook = std::panic::take_hook();
         std::panic::set_hook(Box::new(move |info| {
             if actix_rt::System::is_registered() {
-                let exit_code = if CAUGHT_SIGINT.load(Ordering::SeqCst) { 130 } else { 1 };
-                actix_rt::System::current().stop_with_code(exit_code);
+                actix_rt::System::current().stop_with_code(1);
             }
             default_hook(info);
         }));
     });
 
-    static TRAP_SIGINT_HOOK: std::sync::Once = std::sync::Once::new();
-
-    // This is a workaround to ensure all threads get the exit memo.
-    // Plainly polling ctrl_c() on busy threads like ours can be problematic.
-    TRAP_SIGINT_HOOK.call_once(|| {
-        std::thread::Builder::new()
-            .name("SIGINT trap".into())
-            .spawn(|| {
-                let sys = actix_rt::System::new();
-                sys.block_on(async {
-                    signal::ctrl_c().await.expect("failed to listen for SIGINT");
-                    CAUGHT_SIGINT.store(true, Ordering::SeqCst);
-                });
-                sys.run().unwrap();
-            })
-            .expect("failed to spawn SIGINT handler thread");
-    });
     actix_rt::System::new()
 }
 
 pub fn block_on_interruptible<F: std::future::Future>(
     sys: &actix_rt::SystemRunner,
     f: F,
 ) -> F::Output {
-    sys.block_on(handle_interrupt!(f))
+    sys.block_on(f)
 }
 
 pub fn run_actix<F: std::future::Future>(f: F) {