RFR: 8367848: Parallel: Use NMethodToOopClosure during Young GC

Wed Sep 17 09:07:00 UTC 2025

Replace `MarkingNMethodClosure` with `NMethodToOopClosure` during young-gc. After that, a new local `ThreadsClaimTokenScope` is introduced instead of `StrongRootsScope` to make the thread-claim-token logic visible in the current context.

Test: tier1-3

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Commit messages:
 - pgc-nmethod

Changes: https://git.openjdk.org/jdk/pull/27336/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27336&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367848
  Stats: 11 lines in 1 file changed: 8 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/27336.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27336/head:pull/27336

PR: https://git.openjdk.org/jdk/pull/27336