[wpiutil, wpilib] Add FileLogger and log console output (#6977)

wpiutil/src/main/java/edu/wpi/first/util/WPIUtilJNI.java

@@ -217,6 +217,24 @@ public class WPIUtilJNI {
   public static native int[] waitForObjectsTimeout(int[] handles, double timeout)
       throws InterruptedException;
 
+  /**
+   * Create a native FileLogger. When the specified file is modified, appended data will be appended
+   * to the specified data log.
+   *
+   * @param file path to the file
+   * @param log data log implementation handle
+   * @param key log key to append data to
+   * @return The FileLogger handle.
+   */
+  public static native long createFileLogger(String file, long log, String key);
+
+  /**
+   * Free a native FileLogger. This causes the FileLogger to stop appending data to the log.
+   *
+   * @param fileTail The FileLogger handle.
+   */
+  public static native void freeFileLogger(long fileTail);
+
   /** Utility class. */
   protected WPIUtilJNI() {}
 }