RFR: 8234502: Merge GenCollectedHeap and SerialHeap [v5]

[Lei Zaakjyu]

> 8234502: Merge GenCollectedHeap and SerialHeap

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

  resolve conflict

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16927/files
  - new: https://git.openjdk.org/jdk/pull/16927/files/fef7f8af..e6d7dfed

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16927&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16927&range=03-04

  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16927.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16927/head:pull/16927

PR: https://git.openjdk.org/jdk/pull/16927