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.

wpilibcExamples/src/main/cpp/templates/robotbaseskeleton/cpp/Robot.cpp

@@ -32,7 +32,7 @@ void Robot::StartCompetition() {
   // Tell the DS that the robot is ready to be enabled
   HAL_ObserveUserProgramStarting();
 
-  while (true) {
+  while (!m_exit) {
     if (IsDisabled()) {
       m_ds.InDisabled(true);
       Disabled();
@@ -61,6 +61,8 @@ void Robot::StartCompetition() {
   }
 }
 
+void Robot::EndCompetition() { m_exit = true; }
+
 #ifndef RUNNING_FRC_TESTS
 int main() { return frc::StartRobot<Robot>(); }
 #endif

wpilibcExamples/src/main/cpp/templates/robotbaseskeleton/include/Robot.h

@@ -7,6 +7,8 @@
 
 #pragma once
 
+#include <atomic>
+
 #include <frc/RobotBase.h>
 
 class Robot : public frc::RobotBase {
@@ -18,4 +20,8 @@ class Robot : public frc::RobotBase {
   void Test();
 
   void StartCompetition() override;
+  void EndCompetition() override;
+
+ private:
+  std::atomic<bool> m_exit{false};
 };