Kernel: Add timeout support to Thread::wait_on

This change plumbs a new optional timeout option to wait_on.
The timeout is enabled by enqueing a timer on the timer queue
while we are waiting. We can then see if we were woken up or
timed out by checking if we are still on the wait queue or not.

Kernel/Lock.cpp

@@ -65,7 +65,8 @@ void Lock::lock(Mode mode)
                 m_lock.store(false, AK::memory_order_release);
                 return;
             }
-            Thread::current->wait_on(m_queue, &m_lock, m_holder, m_name);
+            timeval* timeout = nullptr;
+            Thread::current->wait_on(m_queue, timeout, &m_lock, m_holder, m_name);
         }
     }
 }