RFR: 8365922: Parallel: Group uses of GCTimeRatio to a single location

Thu Aug 21 11:01:22 UTC 2025

Unify all accesses of `GCTimeRatio` to a single place so that Parallel gets a coherence view of its value within the pause, if the global variable's value is ever changed.

Test: tier1-3

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Commit messages:
 - pgc-gc-time-ratio-prepare-management

Changes: https://git.openjdk.org/jdk/pull/26881/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26881&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365922
  Stats: 42 lines in 5 files changed: 14 ins; 18 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/26881.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26881/head:pull/26881

PR: https://git.openjdk.org/jdk/pull/26881