RFR: 8335147: Serial: Refactor TenuredGeneration::promote [v2]

[Albert Mingkun Yang]

> Trivial extracting "copying" logic from old-gen-allocation method to unify the use of `Copy` and `transform_stack_chunk` in young-gc promotion path.

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 two additional commits since the last revision:

 - Merge branch 'master' into s1-alloc-promote
 - s1-alloc-promote

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19899/files
  - new: https://git.openjdk.org/jdk/pull/19899/files/10e5e4a3..50ad509c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19899&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19899&range=00-01

  Stats: 4381 lines in 88 files changed: 2671 ins; 1234 del; 476 mod
  Patch: https://git.openjdk.org/jdk/pull/19899.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19899/head:pull/19899

PR: https://git.openjdk.org/jdk/pull/19899