RFR: JDK-8234502 : Merge GenCollectedHeap and SerialHeap [v2]

[Lei Zaakjyu]

> JDK-8234502 : Merge GenCollectedHeap and SerialHeap

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

  include 'serialVMOperations.hpp'

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16623/files
  - new: https://git.openjdk.org/jdk/pull/16623/files/08f1f0a8..4e74cc25

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16623&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16623&range=00-01

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