RFR: JDK-8234502 : Merge GenCollectedHeap and SerialHeap [v3]

[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 'young_gen' function in 'genCollectedHeap.cpp'

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16623/files
  - new: https://git.openjdk.org/jdk/pull/16623/files/4e74cc25..883dd7b1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16623&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16623&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 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