RFR: 8375626: G1: Convert G1CollectionSetChooser to use Atomic<T>

[Thomas Schatzl]

Hi all,

  please review this change to use `Atomic<T>` for the `G1CollectionSetChooser` class.

Testing: gha

Thanks,
  Thomas

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

Commit messages:
 - 8375626

Changes: https://git.openjdk.org/jdk/pull/29298/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29298&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375626
  Stats: 11 lines in 2 files changed: 2 ins; 1 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/29298.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29298/head:pull/29298

PR: https://git.openjdk.org/jdk/pull/29298