RFR: 8376335: Convert PreservedMarks classes to use Atomic<T> [v2]

[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

Thomas Schatzl has updated the pull request incrementally with two additional commits since the last revision:

 - * improve docs
 - * stefank review

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29422/files
  - new: https://git.openjdk.org/jdk/pull/29422/files/a811bc09..226cd455

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29422&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29422&range=00-01

  Stats: 10 lines in 2 files changed: 2 ins; 4 del; 4 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