[11u] RFR 8185525: Add JFR event for DictionarySizes

[Denghui Dong]

Hi all,
  Please review this backport, original patch doesn't apply cleanly, because
SymbolTable has made some changes in upstream (I think it's not necessary to backport those changes) 
and class ClassLoaderDataGraph is located in different files.
11u-webrev:
http://cr.openjdk.java.net/~wzhuo/8185525/webrev.00/
Original bug:
https://bugs.openjdk.java.net/browse/JDK-8185525
 http://hg.openjdk.java.net/jdk/jdk/rev/865ec913f916
Testing: test/jdk/jdk/jfr/event/runtime/TestTableStatisticsEvent.java

Thanks,
Denghui Dong