RFR: 8329658: Serial: Refactor ContiguousSpace::_next_compaction_space [v2]

[Guoxiong Li]

> Hi all,
> 
> This patch removes the uncessary `ContiguousSpace::_next_compaction_space` and uses `DefNewGeneration::_promotion_failed` instead.
> 
> The tests `make test-tier1_gc` passed locally.
> 
> Thanks for taking the time to review.
> 
> Best Regards,
> -- Guoxiong

Guoxiong Li has updated the pull request incrementally with two additional commits since the last revision:

 - Make promotion_failed as private.
 - Judge whether to-space is empty.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18666/files
  - new: https://git.openjdk.org/jdk/pull/18666/files/ebd19ab7..31eae623

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18666&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18666&range=00-01

  Stats: 4 lines in 2 files changed: 1 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18666.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18666/head:pull/18666

PR: https://git.openjdk.org/jdk/pull/18666