Integrated: 8335865: Shenandoah: Improve THP pretouch after JDK-8315923

[William Kemper]

Clean backport.

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Commit messages:
 - Backport 84c3065e8004122f3455a8c28c8719b2c8111c17

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/125/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=125&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335865
  Stats: 18 lines in 1 file changed: 0 ins; 17 del; 1 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/125.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/125/head:pull/125

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/125