Update how unstarted event loop v threads are created (Fixes #49)

Author: franz1981

core/src/main/java/io/netty/loom/EventLoopScheduler.java

@@ -93,9 +93,16 @@ private static ThreadFactory newEventLoopSchedulerFactory(SharedRef sharedRef) {
 		// and share it between the thread attachment and the SchedulingContext,
 		// enabling
 		// work-stealing to change it for both
-		return runnable -> NettyScheduler.newEventLoopScheduledThread(() -> ScopedValue
-				.where(CURRENT_SCHEDULER, new SchedulingContext(Thread.currentThread().threadId(), sharedRef))
-				.run(runnable), sharedRef);
+		var unstartedBuilder = Thread.ofVirtual();
+		// we're not enforcing a preferred carrier on purpose, despite we could - to prevent leaks to happen:
+		// once this scheduler is gone, but a virtual thread is still to complete, we would like to offload it
+		// to the default scheduler rather than trying to reuse this scheduler's carrier thread
+		return runnable -> unstartedBuilder.unstarted(() -> runWithContext(runnable, sharedRef), null, sharedRef);
+	}
+
+	private static void runWithContext(Runnable runnable, SharedRef sharedRef) {
+		ScopedValue.where(CURRENT_SCHEDULER, new SchedulingContext(Thread.currentThread().threadId(), sharedRef))
+				.run(runnable);
 	}
 
 	int externalContinuationsCount() {

core/src/main/java/io/netty/loom/NettyScheduler.java

@@ -117,10 +117,6 @@ public void onContinue(Thread.VirtualThreadTask virtualThreadTask) {
 		jdkBuildinScheduler.onContinue(virtualThreadTask);
 	}
 
-	static Thread newEventLoopScheduledThread(Runnable task, SharedRef sharedRef) {
-		return Thread.VirtualThreadScheduler.newThread(task, sharedRef);
-	}
-
 	public static boolean perCarrierPollers() {
 		return ensureInstalled().perCarrierPollers;
 	}