RFR: 8368261: Serial: Use more precise nmethod scope during Full GC marking [v2]

[Albert Mingkun Yang]

> Small patch of extracting out the nmethod-marking-scope logic in Serial full-gc. The new `NMethodMarkingScope` is placed in `nmethod.hpp` like its counterpart `ThreadsClaimTokenScope`.
> 
> The new `struct` is almost identical to the existing `MarkScope`, so there is a planned followup PR that will address all other users of `StrongRootsScope` to use the recently introduced `ThreadsClaimTokenScope` and the new `NMethodMarkingScope` introduced in this PR, which would make it less abtract than the name `StrongRootsScope`.
> 
> Test: tier1-3

Albert Mingkun Yang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - review
 - Merge branch 'master' into sgc-nmethod-scope
 - sgc-nmethod-scope

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/27423/files
  - new: https://git.openjdk.org/jdk/pull/27423/files/13d0772f..bd641747

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27423&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27423&range=00-01

  Stats: 17512 lines in 472 files changed: 8113 ins; 6611 del; 2788 mod
  Patch: https://git.openjdk.org/jdk/pull/27423.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27423/head:pull/27423

PR: https://git.openjdk.org/jdk/pull/27423