[wpilib] RobotController: Add isSystemTimeValid() (#5696)

This returns true when the system date/time (wall clock) is valid.

hal/src/main/java/edu/wpi/first/hal/HAL.java

@@ -190,6 +190,14 @@ public final class HAL extends JNIWrapper {
    */
   public static native boolean getRSLState();
 
+  /**
+   * Gets if the system time is valid.
+   *
+   * @return True if the system time is valid, false otherwise
+   * @see "HAL_GetSystemTimeValid"
+   */
+  public static native boolean getSystemTimeValid();
+
   /**
    * Gets a port handle for a specific channel and module.
    *