[hal] Add GetTeamNumber (#5596)

wpilibc/src/main/native/include/frc/RobotController.h

@@ -63,6 +63,13 @@ class RobotController {
    */
   static std::string GetComments();
 
+  /**
+   * Returns the team number configured for the robot controller.
+   *
+   * @return team number, or 0 if not found.
+   */
+  static int32_t GetTeamNumber();
+
   /**
    * Read the microsecond-resolution timer on the FPGA.
    *