RFR: 8376199: Convert CodeCacheUnloadingTask to use Atomic<T>

[Thomas Schatzl]

Hi all,

  please review this change to convert usages of `AtomicAccess` to `Atomic<T>` in the `CodeCacheUnloadingTask` class.

Testing: gha

Thanks,
  Thomas

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Commit messages:
 - 8376199

Changes: https://git.openjdk.org/jdk/pull/29418/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29418&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376199
  Stats: 7 lines in 2 files changed: 1 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/29418.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29418/head:pull/29418

PR: https://git.openjdk.org/jdk/pull/29418