[jdk16u] RFR: 8261483: jdk/dynalink/TypeConverterFactoryMemoryLeakTest.java failed with "AssertionError: Should have GCd a method handle by now"

[Attila Szegedi]

Backporting this to eliminate flakiness of tests

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Commit messages:
 - 8261483: jdk/dynalink/TypeConverterFactoryMemoryLeakTest.java failed with "AssertionError: Should have GCd a method handle by now"

Changes: https://git.openjdk.java.net/jdk16u/pull/68/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16u&pr=68&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261483
  Stats: 92 lines in 2 files changed: 71 ins; 8 del; 13 mod
  Patch: https://git.openjdk.java.net/jdk16u/pull/68.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16u pull/68/head:pull/68

PR: https://git.openjdk.java.net/jdk16u/pull/68