RFR: 8274753: ZGC: SEGV in MetaspaceShared::link_shared_classes

[Coleen Phillimore]

This change replaces the Handles with OopHandles in CollectCLDClasses so they don't get GC'd.  Handles aren't good enough because of the HandleMark in ClassLoaderDataGraphIterator.   It also fixes the issue with leaving stale error klass in the dumptime_table and adds a test.
Tested with tier1-6.

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Commit messages:
 - Add test with ZGC fails without fix.
 - 8274753: ZGC: SEGV in MetaspaceShared::link_shared_classes

Changes: https://git.openjdk.java.net/jdk/pull/5859/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5859&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274753
  Stats: 38 lines in 3 files changed: 29 ins; 1 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5859.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5859/head:pull/5859

PR: https://git.openjdk.java.net/jdk/pull/5859