RFR: 8325767: Serial: Move transform_stack_chunk out of TenuredGeneration::promote

[Albert Mingkun Yang]

Trivial a method call from callee to caller.

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Commit messages:
 - trivial

Changes: https://git.openjdk.org/jdk/pull/17836/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17836&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325767
  Stats: 6 lines in 2 files changed: 1 ins; 5 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17836.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17836/head:pull/17836

PR: https://git.openjdk.org/jdk/pull/17836