RFR(xs): 8199667: Unify metaspace list index handling and reinstantiate ChunkManager listindex gtest

[Thomas Stüfe]

Hi all,

may I please have reviews for the following patch:

Bug: https://bugs.openjdk.java.net/browse/JDK-8199667
webrev:
http://cr.openjdk.java.net/~stuefe/webrevs/8199667-unify-chunkindex-helper-functions/webrev.00/webrev/

This is a small cleanup and it reinstates and enhances a small gtest which
was accidentally removed with  8198423.

Thank you, Thomas