RFR: 8373876: StackWalkNativeToJava print more output in case of failures

[Matthias Baesken]

In case of failures the jtreg test StackWalkNativeToJava misses to print the 'bad' output we check. This makes analyzing errors hard, so better enhance the output .
The other checks ` output.shouldNotContain`   print already the diagnostic summary of output.

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Commit messages:
 - JDK-8373876

Changes: https://git.openjdk.org/jdk/pull/28871/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28871&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373876
  Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28871.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28871/head:pull/28871

PR: https://git.openjdk.org/jdk/pull/28871