RFR: 8367417: Serial: Use NMethodToOopClosure during Young GC

[Thomas Schatzl]

On Thu, 11 Sep 2025 13:07:11 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Change `MarkingNMethodClosure` to `NMethodToOopClosure` in young-gc, because no marking is done during young-gc. After that, `StrongRootsScope` becomes unnecessary as well, it's essentially calling `oops_do_marking_epilogue` to undo the effect of `MarkingNMethodClosure`.
> 
> Test: tier1-5

Marked as reviewed by tschatzl (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/27226#pullrequestreview-3228361569