RFR: 8376356: Parallel: Convert PSCardTable to use Atomic<T>

[Thomas Schatzl]

Hi all,

  please review this change to convert `PSCardTable` to use `Atomic<T>`.

Testing: gha

Thanks,
  Thomas

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Commit messages:
 - 8376356

Changes: https://git.openjdk.org/jdk/pull/29428/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29428&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376356
  Stats: 6 lines in 2 files changed: 1 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/29428.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29428/head:pull/29428

PR: https://git.openjdk.org/jdk/pull/29428