RFR: 8329658: Serial: Refactor ContiguousSpace::_next_compaction_space [v5]

[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 with a new target base due to a merge or a rebase. The pull request now contains seven commits:

 - Use a local variable.
 - Merge branch 'master' into NEXT_COMPACT_SPACE
 - Polish
 - Merge branch 'master' into NEXT_COMPACT_SPACE
   
   # Conflicts:
   #	src/hotspot/share/gc/shared/space.hpp
 - Make promotion_failed as private.
 - Judge whether to-space is empty.
 - JDK-8329658

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Changes: https://git.openjdk.org/jdk/pull/18666/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18666&range=04
  Stats: 32 lines in 4 files changed: 0 ins; 31 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