Backport PR #17138 to 9.0: Update container acceptance tests with stdout/stderr changes

[github-actions]

Backport PR #17138 to 9.0 branch, original message:

---

Release notes

[rn:skip]

What does this PR do?

In #17125 jvm setup was redirected to stderr to avoid polluting stdout. This test was actually having to do some additional processing to parse that information. Now that we have split the destinations the tests can be simplified to look for the data they are trying to validate on the appropriate stream.

Why is it important/What is the impact to the user?

No user impact, just a test fix.

Checklist

• My code follows the style guidelines of this project
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have made corresponding changes to the documentation
  - [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
  - [ ] I have added tests that prove my fix is effective or that my feature works

Related issues

• entrypoint: avoid polluting stdout #17125

Failing tests

Failures:
--
  |  
  | 1) A container running the wolfi image behaves like the container is configured correctly logstash should run with the bundled JDK
  | Failure/Error: DEFAULT_FAILURE_NOTIFIER = lambda { \|failure, _opts\| raise failure }
  |  
  | expected "logstash 9.1.0" to match /Using bundled JDK: \/usr\/share\/logstash\/jdk/
  | Diff:
  | @@ -1 +1 @@
  | -/Using bundled JDK: \/usr\/share\/logstash\/jdk/
  | +"logstash 9.1.0"
  |  
  | Shared Example Group: "the container is configured correctly" called from ./docker/spec/wolfi/container_spec.rb:8
  | # ./docker/shared_examples/container.rb:27:in `block in <main>'
  |  
  | Finished in 9 minutes 26 seconds (files took 2.6 seconds to load)

[mashhurs]

LGTM~

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: b215284

Failed CI Steps

• 🥼 Integration Tests / part 1