[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.

wpilibcExamples/src/main/cpp/examples/ArmBotOffboard/include/ExampleSmartMotorController.h

@@ -79,6 +79,4 @@ class ExampleSmartMotorController : public frc::SpeedController {
   void Disable() override {}
 
   void StopMotor() override {}
-
-  void PIDWrite(double output) override {}
 };

wpilibcExamples/src/main/cpp/examples/DriveDistanceOffboard/include/ExampleSmartMotorController.h

@@ -80,8 +80,6 @@ class ExampleSmartMotorController : public frc::SpeedController {
 
   void StopMotor() override {}
 
-  void PIDWrite(double output) override {}
-
  private:
   double m_value = 0.0;
 };

wpilibcExamples/src/main/cpp/examples/ElevatorTrapezoidProfile/include/ExampleSmartMotorController.h

@@ -79,6 +79,4 @@ class ExampleSmartMotorController : public frc::SpeedController {
   void Disable() override {}
 
   void StopMotor() override {}
-
-  void PIDWrite(double output) override {}
 };

wpilibcExamples/src/main/cpp/examples/PacGoat/cpp/subsystems/DriveTrain.cpp

@@ -24,10 +24,6 @@ DriveTrain::DriveTrain() : frc::Subsystem("DriveTrain") {
   m_leftCIMs.SetInverted(true);
   m_rightCIMs.SetInverted(true);
 
-  // Configure encoders
-  m_rightEncoder.SetPIDSourceType(frc::PIDSourceType::kDisplacement);
-  m_leftEncoder.SetPIDSourceType(frc::PIDSourceType::kDisplacement);
-
 #ifndef SIMULATION
   // Converts to feet
   m_rightEncoder.SetDistancePerPulse(0.0785398);

wpilibcExamples/src/main/cpp/examples/PacGoat/cpp/subsystems/Pivot.cpp

@@ -27,7 +27,7 @@ double Pivot::ReturnPIDInput() {
 }
 
 void Pivot::UsePIDOutput(double output) {
-  m_motor.PIDWrite(output);
+  m_motor.Set(output);
 }
 
 bool Pivot::IsAtUpperLimit() {