RFR: 8355369: Remove setAccessible usage for setting final fields in java.util.concurrent

[Viktor Klang]

This Pull Request replaces the uses of Field + setAccessible to modify final fields in java.util.concurrent with Unsafe.

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Commit messages:
 - Update ConcurrentSkipListSet, CopyOnWriteArrayList, and AtomicReferenceArray to use Unsafe rather than Field.setAccessible

Changes: https://git.openjdk.org/jdk/pull/24821/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24821&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355369
  Stats: 29 lines in 3 files changed: 4 ins; 6 del; 19 mod
  Patch: https://git.openjdk.org/jdk/pull/24821.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24821/head:pull/24821

PR: https://git.openjdk.org/jdk/pull/24821