RFR: 8374190: Convert ConcurrentHashTable atomic lists to use Atomic<T>

[Kim Barrett]

Please review this change to ConcurrentHashTable to use `Atomic<Node*>` for
the Node lists.  Note that this does not complete the replacement of direct
uses of AtomicAccess by that class; there's still one more group remaining.

Testing: mach5 tier1-3

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Commit messages:
 - atomic _first & _next

Changes: https://git.openjdk.org/jdk/pull/28951/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28951&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8374190
  Stats: 40 lines in 2 files changed: 12 ins; 0 del; 28 mod
  Patch: https://git.openjdk.org/jdk/pull/28951.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28951/head:pull/28951

PR: https://git.openjdk.org/jdk/pull/28951