RFR: 8234502: Merge GenCollectedHeap and SerialHeap [v6]

[Lei Zaakjyu]

> 8234502: Merge GenCollectedHeap and SerialHeap

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

  remove 'GenCollectedHeap' from 'jdk.hotspot.agent'

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16927/files
  - new: https://git.openjdk.org/jdk/pull/16927/files/e6d7dfed..f6ca5177

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16927&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16927&range=04-05

  Stats: 293 lines in 6 files changed: 89 ins; 190 del; 14 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