RFR: 8204585: Remove IN_ARCHIVE_ROOT from Access API

[Kim Barrett]

Please review this change to the implementation of CDS support to use
a new collector-based protocol for handling archived Java mirrors.
Rather than using the IN_ARCHIVE_ROOT feature of the Access API, we
instead use a new protocol provided by the collected heap (only
G1CollectedHeap for now, since only G1 supports this feature).  This
allows IN_ARCHIVE_ROOT to be removed from the Access API.

This changeset is based on work by Stefan Karlsson.

CR:
https://bugs.openjdk.java.net/browse/JDK-8204585

Webrev:
http://cr.openjdk.java.net/~kbarrett/8204585/open.00/

Testing:
mach5 tier1,2,3, hs-tier4,5.
Local testing of hotspot_cds and hotspot_appcds.