[jdk21u-dev] RFR: 8346713: [testsuite] NeverActAsServerClassMachine breaks TestPLABAdaptToMinTLABSize.java TestPinnedHumongousFragmentation.java TestPinnedObjectContents.java

[Jan Kratochvil]

Only `TestPLABAdaptToMinTLABSize.java` is a clean backport.
`TestPinnedHumongousFragmentation.java` and `TestPinnedObjectContents.java` did not exist in JDK 21.

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Commit messages:
 - 8346713: [testsuite] NeverActAsServerClassMachine breaks TestPLABAdaptToMinTLABSize.java TestPinnedHumongousFragmentation.java TestPinnedObjectContents.java

Changes: https://git.openjdk.org/jdk21u-dev/pull/1277/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1277&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346713
  Stats: 19 lines in 1 file changed: 13 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1277.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1277/head:pull/1277

PR: https://git.openjdk.org/jdk21u-dev/pull/1277