RFR: 8330003: Serial: Move the logic of FastEvacuateFollowersClosure to SerialHeap

[Guoxiong Li]

Hi all,

This patch moves the content of `FastEvacuateFollowersClosure::do_void` to `SerialHeap::scan_evacuated_objs`.

Thanks for taking the time to review.

Best Regards,
-- Guoxiong

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

Commit messages:
 - JDK-8330003

Changes: https://git.openjdk.org/jdk/pull/18725/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18725&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330003
  Stats: 15 lines in 3 files changed: 11 ins; 3 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18725.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18725/head:pull/18725

PR: https://git.openjdk.org/jdk/pull/18725