Run lib.profiler unit tests in CI

[wilx]

This follows up on the review discussion in #9497 by adding the profiler/lib.profiler unit tests to the main CI workflow.

The new CI step runs the existing test-unit target while disabling compilation of the legacy QA-functional source set, which is not executed by that target.

The legacy CPU snapshot tests now use deterministic SampledThreadInfo fixtures for the builder logic. A focused test still exercises the public ThreadInfo[] adapter with data from ThreadMXBean, without relying on private JDK constructors, fields, or internal sun.management classes.

The heap-dump golden output is made deterministic by sorting system-property names and escaping embedded line breaks. The golden file is refreshed for that stable representation and the current JVM's floating-point string representation.

Validation:

JAVA_HOME=/usr/lib/jvm/java-21-openjdk-amd64 ant -f profiler/lib.profiler test-unit -Ddisable.qa-functional.tests=true

69 tests passed with no failures or errors.

Assisted-by: OpenAI GPT-5 Codex

---

^Add meaningful description above

Click to collapse/expand PR instructions

By opening a pull request you confirm that, unless explicitly stated otherwise, the changes -

• are all your own work, and you have the right to contribute them.
• are contributed solely under the terms and conditions of the Apache License 2.0 (see section 5 of the license for more information).

LLMs, Commit messages and PR description:

• Please make sure (eg. git log) that all commits have a valid name and email address for you in the Author field.
• LLM assisted commits should be attributed with an Assisted-by: MODEL_NAME MODEL_VERSION line appended to the commit message.
  • Please mention coding assistance in the PR description too (eg. by adding the same Assisted-by line from above)
  • Please describe the changes in your own words - we'd like to know you understand the changes being made!

If you're a first time contributor, see the Contributing guidelines for more information.

If you're a committer, please label the PR before pressing "Create pull request" so that the right test jobs can run.

PR approval and merge checklist:

1. Was this PR correctly labeled, did the right tests run? When did they run?
2. Is this PR squashed?
3. Are author name / email address correct? Are co-authors correctly listed? Do the commit messages need updates?
4. Does the PR title and description still fit after the Nth iteration? Is the description sufficient to appear in the release notes?

If this PR targets the delivery branch: don't merge. (full wiki article)