Kernel: Use a dedicated thread state for wait-queued threads

Instead of using the generic block mechanism, wait-queued threads now
go into the special Queued state.

This fixes an issue where signal dispatch would unblock a wait-queued
thread (because signal dispatch unblocks blocked threads) and cause
confusion since the thread only expected to be awoken by the queue.

Kernel/Lock.cpp

@@ -19,7 +19,7 @@ void Lock::lock()
                 return;
             }
             m_lock.store(false, AK::memory_order_release);
-            (void)current->donate_remaining_timeslice_and_block<Thread::WaitQueueBlocker>(m_holder, m_name, m_queue);
+            current->wait_on(m_queue, m_holder, m_name);
         }
     }
 }