Currently, we have functions like TeleopInit() for running code on mode
entry, but no such functions for running code on mode exit, and it's
cumbersome to add those in user code without making a custom robot
class. This PR adds exit functions to TimedRobot.
Some example use cases include DisabledExit() for operations when the
robot enables (whether that be into teleop, autonomous, or test) and
AutonomousExit() for disabling feedback controllers.
Currently, teams have to make a Notifier to run feedback controllers
more often than the TimedRobot loop period of 20ms (running TimedRobot
more often than this is not advised). This lets users add callbacks to
the main robot loop that run at a user-defined period. This allows
running feedback controllers more often, but does so synchronously with
TimedRobot so there aren't any thread safety issues.
To make the tests reliable, the synchronization in simulation Notifiers
had to be reworked. StepTiming() now waits for all Notifiers to reach
HAL_WaitForNotifierAlarm(), then steps the time, then lets any expired
Notifiers run.
While there, we made some variable names more descriptive and added more
comments.
