RFR: 8188075: [Nestmates] Add a core reflection API to get nestmate information

[David Holmes]

bug: https://bugs.openjdk.java.net/browse/JDK-8188075

webrev: http://cr.openjdk.java.net/~dholmes/8188075/webrev.full/index.html

The Nestmate core reflection API was discussed on the EG list:

http://mail.openjdk.java.net/pipermail/valhalla-spec-experts/2017-November/000411.html

so any concerns about the API itself should be discussed there or on the 
observers list please - thank you.

This is the implementation of that API in java.lang.Class and 
implemented in the JVM, together with an extensive set of tests.

Thanks,
David