[wpilib] Document simulation APIs (#3079)

- Remove sim checkstyle suppression
- Add [[nodiscard]] to C++ register callback functions
- Add a couple of missing sim functions

Co-authored-by: Peter Johnson <johnson.peter@gmail.com>
Co-authored-by: Starlight220 <yotamshlomi@gmail.com>

wpilibc/src/main/native/include/frc/simulation/AnalogOutputSim.h

@@ -33,20 +33,57 @@ class AnalogOutputSim {
    */
   explicit AnalogOutputSim(int channel);
 
-  std::unique_ptr<CallbackStore> RegisterVoltageCallback(
+  /**
+   * Register a callback to be run whenever the voltage changes.
+   *
+   * @param callback the callback
+   * @param initialNotify whether to call the callback with the initial state
+   * @return the CallbackStore object associated with this callback
+   */
+  [[nodiscard]] std::unique_ptr<CallbackStore> RegisterVoltageCallback(
       NotifyCallback callback, bool initialNotify);
 
+  /**
+   * Read the analog output voltage.
+   *
+   * @return the voltage on this analog output
+   */
   double GetVoltage() const;
 
+  /**
+   * Set the analog output voltage.
+   *
+   * @param voltage the new voltage on this analog output
+   */
   void SetVoltage(double voltage);
 
-  std::unique_ptr<CallbackStore> RegisterInitializedCallback(
+  /**
+   * Register a callback to be run when this analog output is initialized.
+   *
+   * @param callback the callback
+   * @param initialNotify whether to run the callback with the initial state
+   * @return the CallbackStore object associated with this callback
+   */
+  [[nodiscard]] std::unique_ptr<CallbackStore> RegisterInitializedCallback(
       NotifyCallback callback, bool initialNotify);
 
+  /**
+   * Check whether this analog output has been initialized.
+   *
+   * @return true if initialized
+   */
   bool GetInitialized() const;
 
+  /**
+   * Define whether this analog output has been initialized.
+   *
+   * @param initialized whether this object is initialized
+   */
   void SetInitialized(bool initialized);
 
+  /**
+   * Reset all simulation data on this object.
+   */
   void ResetData();
 
  private: