[jdk25] RFR: 8357976: GenShen crash in swap_card_tables: Should be clean

[William Kemper]

Clean backport. Fixes correctness issue in Shenandoah.

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Commit messages:
 - Backport 382f870cd53d69dfc1d2b96150aa2c026e47f642

Changes: https://git.openjdk.org/jdk/pull/26246/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26246&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357976
  Stats: 17 lines in 2 files changed: 10 ins; 4 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/26246.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26246/head:pull/26246

PR: https://git.openjdk.org/jdk/pull/26246