[AbstractWorkStealingScheduler] Emit warning if queue is full

In case pushing to the local work-stealing queue fails because the
queue is full, and that failure is not fatal as it is in Fibril, emit
a warning once.

emper/strategies/AbstractWorkStealingScheduler.cpp

@@ -294,6 +294,9 @@ auto AbstractWorkStealingScheduler::pushBottom(AbstractFiber& fiber) -> bool {
 			uint64_t queueLength = pushed.size;
 			awss::stats.recordScheduledToLocalAndQueueLength(queueLength);
 		}
+	} else if (!queueFullWarningEmitted) {
+		queueFullWarningEmitted = true;
+		LOGW("Pushing to queue failed: Queue full");
 	}
 	return pushed;
 }

emper/strategies/AbstractWorkStealingScheduler.hpp

@@ -28,6 +28,8 @@ class AbstractWorkStealingScheduler : public Scheduler {
 	auto nextFiberViaAnywhereQueue() -> std::optional<NextFiberResult>;
 	auto tryStealFiberFrom(workerid_t victim) -> std::optional<NextFiberResult>;
 
+	bool queueFullWarningEmitted = false;
+
  protected:
 	WsQueue<QUEUE_SIZE>** queues;
 	static thread_local WsQueue<QUEUE_SIZE> queue;