Make child-process tests portable across operating systems

[AlexeyKuznetsov-DD]

What Does This Do

Adds PortableCommand so tests can run echo, cat, sleep, and a non-terminating command without OS-specific call sites. POSIX keeps native utilities; Windows uses a small child JVM.

Migrates ProcessSupervisorTest and ShellCommandExecutorTest to the portable commands.

Motivation

Make child-process tests OS-independent without relying on Windows shell builtins or changing existing POSIX behavior.

Additional Notes

Validated the helper on the default JVM and Java 8, plus both migrated test classes: 43 focused test executions passed.

Contributor Checklist

• Format the title according to the contribution guidelines
• Assign the type: and (comp: or inst:) labels in addition to any other useful labels
• Avoid using close, fix, or any linking keywords when referencing an issue
  Use solves instead, and assign the PR milestone to the issue
• Update the CODEOWNERS file on source file addition, migration, or deletion
• Update public documentation with any new configuration flags or behaviors
• Once approved, use merge queue to merge the PR

Jira ticket: N/A

[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	14.82 s	14.79 s	[-0.7%; +1.1%] (no difference)
startup:insecure-bank:tracing:Agent	13.63 s	13.75 s	[-1.7%; -0.1%] (maybe better)
startup:petclinic:appsec:Agent	17.40 s	17.34 s	[-0.7%; +1.4%] (no difference)
startup:petclinic:iast:Agent	16.87 s	17.60 s	[-8.4%; +0.1%] (no difference)
startup:petclinic:profiling:Agent	17.45 s	17.32 s	[-0.3%; +1.7%] (no difference)
startup:petclinic:sca:Agent	17.55 s	17.41 s	[-0.1%; +1.7%] (no difference)
startup:petclinic:tracing:Agent	16.58 s	16.66 s	[-1.4%; +0.5%] (no difference)

Commit: 25626260 · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.