[wpilibc] Transition C++ classes to units::second_t (#3396)

A lot of these are breaking changes. frc::Timer was replaced with the
contents of frc2::Timer. The others were in-place argument changes or
removing deprecated non-unit overloads.

wpilibcExamples/src/main/cpp/examples/MecanumDrivePoseEstimator/cpp/Drivetrain.cpp

@@ -4,7 +4,7 @@
 
 #include "Drivetrain.h"
 
-#include <frc2/Timer.h>
+#include <frc/Timer.h>
 
 #include "ExampleGlobalMeasurementSensor.h"
 
@@ -58,5 +58,5 @@ void Drivetrain::UpdateOdometry() {
   m_poseEstimator.AddVisionMeasurement(
       ExampleGlobalMeasurementSensor::GetEstimatedGlobalPose(
           m_poseEstimator.GetEstimatedPosition()),
-      frc2::Timer::GetFPGATimestamp() - 0.3_s);
+      frc::Timer::GetFPGATimestamp() - 0.3_s);
 }