[jdk17u-dev] RFR: 8324933: ConcurrentHashTable::statistics_calculate synchronization is expensive

[Martin Doerr]

Backport of [JDK-8324933](https://bugs.openjdk.org/browse/JDK-8324933). Clean except NULL vs. nullptr diff in removed code.

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Commit messages:
 - Backport 0e2fdc95ae47c11e6a1e47cdc6190268e29a9d9c

Changes: https://git.openjdk.org/jdk17u-dev/pull/2512/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2512&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8324933
  Stats: 20 lines in 1 file changed: 8 ins; 1 del; 11 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2512.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2512/head:pull/2512

PR: https://git.openjdk.org/jdk17u-dev/pull/2512