Add ability to end startCompetition() main loop (#2032)

This is useful for both cleanly exiting from simulation and for unit testing
at a framework level.

This change required removing move constructor/assignment from IterativeRobot.

wpilibc/src/main/native/cpp/TimedRobot.cpp

@@ -43,6 +43,11 @@ void TimedRobot::StartCompetition() {
   }
 }
 
+void TimedRobot::EndCompetition() {
+  int32_t status = 0;
+  HAL_StopNotifier(m_notifier, &status);
+}
+
 units::second_t TimedRobot::GetPeriod() const {
   return units::second_t(m_period);
 }