RFR: 8368104: Parallel: Refactor PSThreadRootsTaskClosure

[Albert Mingkun Yang]

Trivial changing the closure input arg to avoid `PSPromotionManager` lookup.

Test: tier1

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Commit messages:
 - pgc-young-gc-refactor

Changes: https://git.openjdk.org/jdk/pull/27393/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27393&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368104
  Stats: 13 lines in 1 file changed: 1 ins; 4 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/27393.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27393/head:pull/27393

PR: https://git.openjdk.org/jdk/pull/27393