RFR: 8369013: Shenandoah: passive mode should support enabling ShenandoahCardBarrier [v2]

[Rui Li]

> Add card barriers to passive mode to test out the price of card barriers. 
> 
> How this change is implemented is to instantiate the old region in passive mode - old region owns the card table so this would minimize the code change with a bit price of native memory. It does sound weird to have old gen in passive mode, but since passive mode is a just diagnostic mode, we'll go with it for the cleanliness of the change.

Rui Li has updated the pull request incrementally with one additional commit since the last revision:

  Move write table clean to degen

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27966/files
  - new: https://git.openjdk.org/jdk/pull/27966/files/ecde5211..e6fdbc60

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27966&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27966&range=00-01

  Stats: 11 lines in 2 files changed: 6 ins; 5 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/27966.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27966/head:pull/27966

PR: https://git.openjdk.org/jdk/pull/27966