[jdk22u] RFR: 8321815: Shenandoah: gc state should be synchronized to java threads only once per safepoint

[William Kemper]

Clean backport.

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Commit messages:
 - Backport 808a03927c153581cbece93a4f5a4f8242b61ef5

Changes: https://git.openjdk.org/jdk22u/pull/31/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk22u&pr=31&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321815
  Stats: 41 lines in 5 files changed: 32 ins; 1 del; 8 mod
  Patch: https://git.openjdk.org/jdk22u/pull/31.diff
  Fetch: git fetch https://git.openjdk.org/jdk22u.git pull/31/head:pull/31

PR: https://git.openjdk.org/jdk22u/pull/31