RFR (S): 8235341: Improve WorkerDataArray API to disallow separate instantiation of sub-items

[Thomas Schatzl]

Hi all,

   can I have reviews for this follow-up change of JDK-8235247 that 
improves the API about using sub-items in WorkerDataArray to effectively 
disallow manual handling of them.

This makes it hopefully clear how to use sub-WorkerDataArrays, and 
impossible to use them separately, obviating questions about ownership.

The change is mostly about changing the link_thread_work_items() method 
to internally construct the sub-WorkerDataArray; this results in a lot 
of obsolete code that has been removed here.

This cleanup is followed by a change of the argument order in the 
WorkerDataArray constructor to make the argument order similar to 
link/add_thread_work_items().

CR:
https://bugs.openjdk.java.net/browse/JDK-8235341
Webrev:
http://cr.openjdk.java.net/~tschatzl/8235341/webrev/
Testing:
hs-tier1-3

Thanks,
   Thomas