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

[Satyen Subramaniam]

Renaming `ShenandoahEvacuationInformation.freedRegions` to `ShenandoahEvacuationInformation.freeRegions` for clarity, and fixing incorrect assertion in  TestShenandoahEvacuationInformationEvent.cpp

Tested with tier 1, tier 2, and tier 3 tests.

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Commit messages:
 - Adjusting ShenandoahEvacuationInformation event and test assertions

Changes: https://git.openjdk.org/jdk/pull/23362/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23362&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348610
  Stats: 15 lines in 5 files changed: 2 ins; 1 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/23362.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23362/head:pull/23362

PR: https://git.openjdk.org/jdk/pull/23362