[Shared Tasks] Implement Activity Locking (#2339)

* Add shared task element locking

This adds the `lock_activity_id` field to the tasks table which will
automatically lock a shared task when that element becomes active.

A method was added to world analogous to zone's UnlockActivities to
determine when an activity is active with respect to task steps.

Also adds quest apis to manually lock or unlock a client's shared task

* Add comment

world/shared_task_world_messaging.cpp

@@ -349,6 +349,15 @@ void SharedTaskWorldMessaging::HandleZoneMessage(ServerPacket *pack)
 
 			break;
 		}
+		case ServerOP_SharedTaskLock: {
+			auto buf = reinterpret_cast<ServerSharedTaskLock_Struct*>(pack->pBuffer);
+			auto shared_task = shared_task_manager.FindSharedTaskByTaskIdAndCharacterId(buf->task_id, buf->source_character_id);
+			if (shared_task)
+			{
+				shared_task_manager.LockTask(shared_task, buf->lock);
+			}
+			break;
+		}
 		default:
 			break;
 	}