[wpilib] Remove PIDController, PIDOutput, PIDSource

Move them to the old commands vendordep so that PIDCommand and PIDSubsystem
continue to work.

This also removes Filter and LinearDigitalFilter.

wpilibc/src/main/native/cpp/SpeedControllerGroup.cpp

@@ -60,10 +60,6 @@ void SpeedControllerGroup::StopMotor() {
   }
 }
 
-void SpeedControllerGroup::PIDWrite(double output) {
-  Set(output);
-}
-
 void SpeedControllerGroup::InitSendable(SendableBuilder& builder) {
   builder.SetSmartDashboardType("Speed Controller");
   builder.SetActuator(true);