RFR: JDK-8234502 : Merge GenCollectedHeap and SerialHeap [v6]

[Lei Zaakjyu]

> JDK-8234502 : Merge GenCollectedHeap and SerialHeap

Lei Zaakjyu has updated the pull request incrementally with one additional commit since the last revision:

  fix include statements

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16623/files
  - new: https://git.openjdk.org/jdk/pull/16623/files/bf022a87..1202a7bd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16623&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16623&range=04-05

  Stats: 4 lines in 4 files changed: 2 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16623.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16623/head:pull/16623

PR: https://git.openjdk.org/jdk/pull/16623