Add readBytes method to RandomAccessInput

[iverase]

We can currently read a RandomAccessInput byte by byte but it does not provide a method to bulk read a chunck of bytes, similary to what DataInput provides with DataInput#readBytes(byte[], int, int). Therefore I would like to propose to add it with a default implementation that reads bye per byte:

  /**
   * Reads a specified number of bytes starting at a given position into an array at the specified
   * offset.
   *
   * @see DataInput#readBytes
   */
  default void readBytes(long pos, byte[] bytes, int offset, int length) throws IOException {
    for (int i = 0; i < length; i++) {
      bytes[offset + i] = readByte(pos + i);
    }
  }

We can add faster implementation for all know implementations in Lucene code base.