Debug:Qutex: Add deadlock detection based on elapsed time

We now detect that a deadlock is likely when
CONFIG_DEBUG_QUTEX_DEADLOCK_TIMEOUT_MS has elapsed. This is the
preliminary work required to do a backtrace through the call
stack and figure out if a deadlock has really occured.

To do this, we'd have to go through the async call chain and
search for a previous caller which acquired the same qutex as
the one that first failed during this Lockvoker LockSet acquisition
attempt.

include/lockSet.h

@@ -81,9 +81,12 @@ public:
 	/**
 	 * @brief Try to acquire all locks in order; back off if acquisition fails
 	 * @param lockvoker The LockerAndInvoker attempting to acquire the locks
+	 * @param firstFailedQutex Output parameter to receive the first Qutex that
+	 * 	failed acquisition (can be nullptr)
 	 * @return true if all locks were acquired, false otherwise
 	 */
-	bool tryAcquireOrBackOff(LockerAndInvokerBase &lockvoker);
+	bool tryAcquireOrBackOff(
+		LockerAndInvokerBase &lockvoker, Qutex *firstFailedQutex = nullptr);
 	void unregisterFromQutexQueues();
 
 	/**