RFR: 8347804: GenShen: Crash with small GCCardSizeInBytes and small Java heap [v2]

[Kelvin Nilsen]

> Original implementation was not robust to overriding of CardSizeInBytes, especially to smaller values.  This fixes that issue.

Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:

  Respond to reviewer feedback

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23373/files
  - new: https://git.openjdk.org/jdk/pull/23373/files/7120cdf3..cf06bf0d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23373&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23373&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23373.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23373/head:pull/23373

PR: https://git.openjdk.org/jdk/pull/23373