RFR: 8248216: JFR: Unify handling of all OopStorage instances in LeakProfiler root processing

[Erik Österlund]

Hi,

We want it to be as convenient as possible for the runtime to add new 
OopStorage instances. Therefore, rather than picking specific 
OopStorages during LeakProfiler root processing, the 
OopStorageSet::strong_iterator() should be used instead. That way, once 
a new OopStorage is added to the OopStorageSet, it is automatically 
plugged in to the JFR LeakProfiler.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8248216

Webrev:
http://cr.openjdk.java.net/~eosterlund/8248216/webrev.00/

Thanks,
/Erik