RFR: 8348610: GenShen: TestShenandoahEvacuationInformationEvent failed with setRegions >= regionsFreed: expected 1 >= 57

[William Kemper]

Clean, but contains follow up fix.

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Commit messages:
 - 8349639: jfr/event/gc/detailed/TestShenandoahEvacuationInformationEvent.java fails to compile after JDK-8348610
 - 8348610: GenShen: TestShenandoahEvacuationInformationEvent failed with setRegions >= regionsFreed: expected 1 >= 57

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/164/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=164&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348610
  Stats: 17 lines in 5 files changed: 2 ins; 1 del; 14 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/164.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/164/head:pull/164

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/164