RFR: 8369178: G1: Use NMethodMarkingScope and ThreadsClaimTokenScope in G1RootProcessor

Mon Oct 6 12:27:57 UTC 2025

Replace `StrongRootsScope` with `ThreadsClaimTokenScope` and `MarkingNMethodClosure` in `G1RootProcessor ` to be more precise with what is needed and why.

- `MarkingNMethodClosure` is used in `G1FullGCMarkTask`, so we also need `NMethodMarkingScope`.
- `active_workers ` is guaranteed to be `> 0`

Passes tier1 and tier2 (fastdebug).

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Commit messages:
 - revert
 - replace

Changes: https://git.openjdk.org/jdk/pull/27644/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27644&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8369178
  Stats: 53 lines in 8 files changed: 7 ins; 39 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/27644.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27644/head:pull/27644

PR: https://git.openjdk.org/jdk/pull/27644