RFR: 8376335: Convert PreservedMarks classes to use Atomic<T>

[Thomas Schatzl]

Hi all,

  please review this change to make the `PreservedMarks` classes use `Atomic<T>`.

Some refactoring allowed removal of a now unnecessary function, and imo improved the code, avoiding the somewhat awkward passing of the atomic variable.

Testing: gha, tier1-5

Thanks,
  Thomas

-------------

Commit messages:
 - 8376335

Changes: https://git.openjdk.org/jdk/pull/29422/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29422&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376335
  Stats: 29 lines in 2 files changed: 8 ins; 11 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/29422.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29422/head:pull/29422

PR: https://git.openjdk.org/jdk/pull/29422