[jdk17u-dev] RFR: 8346929: runtime/ClassUnload/DictionaryDependsTest.java fails with "Test failed: should be unloaded"

[Goetz Lindenmaier]

I backport this for parity with 17.0.18-oracle.

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Commit messages:
 - Backport 6e43f48fcf342266b3d50688af7ae4664c018ac8

Changes: https://git.openjdk.org/jdk17u-dev/pull/3921/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3921&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346929
  Stats: 81 lines in 11 files changed: 29 ins; 26 del; 26 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3921.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3921/head:pull/3921

PR: https://git.openjdk.org/jdk17u-dev/pull/3921