RFR: JDK-8234502 : Merge GenCollectedHeap and SerialHeap [v4]

[Lei Zaakjyu]

> JDK-8234502 : Merge GenCollectedHeap and SerialHeap

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

  Completely removed 'GenCollectedHeap'

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16623/files
  - new: https://git.openjdk.org/jdk/pull/16623/files/883dd7b1..8f164430

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16623&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16623&range=02-03

  Stats: 74 lines in 3 files changed: 4 ins; 69 del; 1 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