RFR: 8223504: improve performance of forall loops by better inlining of "iterator()" methods.

[Sergey Kuksenko]

Hi All,

I would like to ask for review the following change/update:

https://bugs.openjdk.java.net/browse/JDK-8223504

http://cr.openjdk.java.net/~skuksenko/hotspot/8223504/webrev.00/

Previous email discussion: 
http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2019-February/032623.html

Obtained performance improvements of forall loops:
Maps (iterating entries, values, keys):
- HashMap - 2x times speedup
- TreeMap - +15%
- ConcurrentHashMap - +16%

Collections:
- HashSet - +13%
- ConcurrentLinkedQueue - +27%
- LinkedList - +8%