RFR: 8355372: GenShen: Test gc/shenandoah/generational/TestOldGrowthTriggers.java fails with UseCompactObjectHeaders enabled

[William Kemper]

Add a test case for `-XX:+UseCompactObjectHeaders`, increase pressure on old generation. I ran the test (which includes a compact object headers case now) fifty times without failure.

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Commit messages:
 - Add test case for compact object headers, increase pressure on old generation

Changes: https://git.openjdk.org/jdk/pull/24888/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24888&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355372
  Stats: 20 lines in 1 file changed: 12 ins; 8 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24888.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24888/head:pull/24888

PR: https://git.openjdk.org/jdk/pull/24888