RFR: 8368599: ShenandoahConcurrentMark could use ThreadsClaimTokenScope [v2]

[Francesco Andreuzzi]

> Replace `StrongRootsScope` with `ThreadsClaimTokenScope` in `ShenandoahConcurrentMark::finish_mark_work` to be more precise with what is actually needed and why. Similar to #27385.
> 
> Test: tier1, and tier[1,2,3]_gc_shenandoah

Francesco Andreuzzi has updated the pull request incrementally with one additional commit since the last revision:

  as field

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27477/files
  - new: https://git.openjdk.org/jdk/pull/27477/files/44377b16..b1686c28

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27477&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27477&range=00-01

  Stats: 4 lines in 1 file changed: 2 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27477.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27477/head:pull/27477

PR: https://git.openjdk.org/jdk/pull/27477