RFR: 8348349: Refactor CDSConfig::is_dumping_heap()

[Ioi Lam]

Please review this small clean up:

`HeapShared::can_write()` and `CDSConfig::is_dumping_heap()` are both for deciding whether CDS should dump heap objects. I removed the former and consolidated all the logic to the latter.

I also updated the logging message in case heap objects cannot be dumped.

I also updated VMProps to clarify what `vmCDSCanWriteArchivedJavaHeap()` means.

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Commit messages:
 - Fixed whitespace
 - Fixed 32-bit build
 - 8348349: Refactor HeapShared::can_write()

Changes: https://git.openjdk.org/jdk/pull/23249/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23249&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348349
  Stats: 117 lines in 12 files changed: 59 ins; 36 del; 22 mod
  Patch: https://git.openjdk.org/jdk/pull/23249.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23249/head:pull/23249

PR: https://git.openjdk.org/jdk/pull/23249