[hal, wpilib] Add brownout voltage configuration (#3632)

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

@@ -394,6 +394,30 @@ class RoboRioSim {
    */
   static void SetUserFaults3V3(int userFaults3V3);
 
+  /**
+   * Register a callback to be run whenever the brownout 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]] static std::unique_ptr<CallbackStore>
+  RegisterBrownoutVoltageCallback(NotifyCallback callback, bool initialNotify);
+
+  /**
+   * Measure the brownout voltage.
+   *
+   * @return the brownout voltage
+   */
+  static units::volt_t GetBrownoutVoltage();
+
+  /**
+   * Define the brownout voltage.
+   *
+   * @param vInVoltage the new voltage
+   */
+  static void SetBrownoutVoltage(units::volt_t brownoutVoltage);
+
   /**
    * Reset all simulation data.
    */