RFR: 8376131: Convert ContiguousSpace to use Atomic<T>

[Thomas Schatzl]

Hi all,

  please review this conversions of `ContiguousSpace` to use `Atomic<T>`.

Testing: gha, tier1-5

Thanks,
  Thomas

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Commit messages:
 - 8376131

Changes: https://git.openjdk.org/jdk/pull/29370/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29370&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376131
  Stats: 21 lines in 4 files changed: 2 ins; 7 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/29370.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29370/head:pull/29370

PR: https://git.openjdk.org/jdk/pull/29370