wpilibc: Add overloads for units (#1815)

Add unit-taking overloads to the following classes:
- IterativeRobotBase
- LinearFilter
- Notifier
- TimedRobot
- Timer (HasPeriodPassed only)
- frc2::PIDController

The corresponding non-units-taking functions have been deprecated.

The return value of TimedRobot::GetPeriod() was updated.
This is a breaking change, users should use to<double> to get the value in seconds.

Other return values, e.g. Timer::Get(), have NOT been updated due to much wider use.

wpilibc/src/main/native/cpp/Notifier.cpp

@@ -96,17 +96,25 @@ void Notifier::SetHandler(std::function<void()> handler) {
 }
 
 void Notifier::StartSingle(double delay) {
+  StartSingle(units::second_t(delay));
+}
+
+void Notifier::StartSingle(units::second_t delay) {
   std::scoped_lock lock(m_processMutex);
   m_periodic = false;
-  m_period = delay;
+  m_period = delay.to<double>();
   m_expirationTime = Timer::GetFPGATimestamp() + m_period;
   UpdateAlarm();
 }
 
 void Notifier::StartPeriodic(double period) {
+  StartPeriodic(units::second_t(period));
+}
+
+void Notifier::StartPeriodic(units::second_t period) {
   std::scoped_lock lock(m_processMutex);
   m_periodic = true;
-  m_period = period;
+  m_period = period.to<double>();
   m_expirationTime = Timer::GetFPGATimestamp() + m_period;
   UpdateAlarm();
 }