Add array type field for JFR Event

[Denghui Dong]

Hi team,
  In the current implementation of JFR, it seems that we can't define array type field for JFR events.
  I have made some changes in GenerateJfrFiles.java so that we can define array type field for native JFR events, it works now.
  Do any others think it's useful?

Thanks,
Denghui Dong