RFR: 8330145: Serial: Refactor SerialHeap::scan_evacuated_objs [v3]

[Albert Mingkun Yang]

> Simple refactoring to extract oop-scanning logic from generation.

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 six additional commits since the last revision:

 - Merge branch 'master' into s1-scan-evac-obj
 - review
 - Merge branch 'master' into s1-scan-evac-obj
 - review
 - Merge branch 'master' into s1-scan-evac-obj
 - s1-scan-evac-obj

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18750/files
  - new: https://git.openjdk.org/jdk/pull/18750/files/eb7a3665..b548701e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18750&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18750&range=01-02

  Stats: 25369 lines in 183 files changed: 13343 ins; 11358 del; 668 mod
  Patch: https://git.openjdk.org/jdk/pull/18750.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18750/head:pull/18750

PR: https://git.openjdk.org/jdk/pull/18750