RFR: 8333356: JVM crashes with "aux_index does not match even or odd indices"

[Coleen Phillimore]

You get this message if the nodes of the concurrent hash table are corrupted or somehow don't yield the same hashcode as when the node was entered in the table.  This change makes the error message less obscure, and in debug mode compares the two hash codes.  The hash code is kept in the table in only debug mode, because we don't want the table to take a lot more memory.
Tested with tier1-4.

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Commit messages:
 - 8333356: JVM crashes with "aux_index does not match even or odd indices"

Changes: https://git.openjdk.org/jdk/pull/20503/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20503&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333356
  Stats: 69 lines in 3 files changed: 68 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20503.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20503/head:pull/20503

PR: https://git.openjdk.org/jdk/pull/20503