[jdk21u-dev] RFR: 8328592: hprof tests fail with -XX:-CompactStrings

[Aleksey Shipilev]

See the bug for symptoms. The tests are failing because hprof test library is confused about non-compact strings.

Additional testing:
 - [x] `serviceability/HeapDump lib-test:all` with `-XX:-CompactStrings` now pass
 - [x]  `serviceability/HeapDump lib-test:all` with `-XX:+CompactStrings` still pass

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Commit messages:
 - Backport bb3e84bd1fd8217fcb319de8a0716e44359e3423

Changes: https://git.openjdk.org/jdk21u-dev/pull/436/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=436&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328592
  Stats: 37 lines in 2 files changed: 29 ins; 1 del; 7 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/436.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/436/head:pull/436

PR: https://git.openjdk.org/jdk21u-dev/pull/436