Revert "Add ParameterEventsSubscriber class (ros2#829)" (ros2#1572)

This reverts commit c8713ed.

Author: nuclearsandwich

rclcpp/CMakeLists.txt

@@ -80,7 +80,6 @@ set(${PROJECT_NAME}_SRCS
   src/rclcpp/parameter.cpp
   src/rclcpp/parameter_value.cpp
   src/rclcpp/parameter_client.cpp
-  src/rclcpp/parameter_event_handler.cpp
   src/rclcpp/parameter_events_filter.cpp
   src/rclcpp/parameter_map.cpp
   src/rclcpp/parameter_service.cpp

rclcpp/include/rclcpp/parameter_event_handler.hpp

@@ -147,15 +147,14 @@
 #include "rclcpp/guard_condition.hpp"
 #include "rclcpp/logging.hpp"
 #include "rclcpp/node.hpp"
-#include "rclcpp/parameter_client.hpp"
-#include "rclcpp/parameter_event_handler.hpp"
 #include "rclcpp/parameter.hpp"
+#include "rclcpp/parameter_client.hpp"
 #include "rclcpp/parameter_service.hpp"
 #include "rclcpp/rate.hpp"
 #include "rclcpp/time.hpp"
 #include "rclcpp/utilities.hpp"
 #include "rclcpp/visibility_control.hpp"
-#include "rclcpp/waitable.hpp"
 #include "rclcpp/wait_set.hpp"
+#include "rclcpp/waitable.hpp"
 
 #endif  // RCLCPP__RCLCPP_HPP_