RFR: 8327854: Test java/util/stream/test/org/openjdk/tests/java/util/stream/WhileOpStatefulTest.java failed with RuntimeException

[Viktor Klang]

This PR improves the test failure output for the failing test case, and the underlying issue is likely going to be addressed by https://github.com/openjdk/jdk/pull/19131 /cc @DougLea

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Commit messages:
 - Improving the failure output of WhileOpStatefulTest

Changes: https://git.openjdk.org/jdk/pull/19508/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19508&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327854
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19508.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19508/head:pull/19508

PR: https://git.openjdk.org/jdk/pull/19508