[oldCommands] Add wrappers for WPILib objects to work with old PID Controller (#3710)

wpilibOldCommands/src/main/native/include/frc/pidwrappers/PIDEncoder.h

@@ -0,0 +1,28 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include "frc/Encoder.h"
+#include "frc/PIDSource.h"
+
+namespace frc {
+
+/**
+ * Wrapper so that PIDSource is implemented for Encoder for old PIDController
+ */
+class PIDEncoder : public PIDSource, public Encoder {
+  using Encoder::Encoder;
+
+ public:
+  /**
+   * Get the PIDOutput for the PIDSource base object. Can be set to return
+   * distance or rate using SetPIDSourceType(). Defaults to distance.
+   *
+   * @return The PIDOutput (distance or rate, defaults to distance)
+   */
+  double PIDGet() override;
+};
+
+}  // namespace frc