Support profile API for PPL

[penghuo]

Description

• Introduce query profiling framework with profile contexts, metrics, and thread-local lifecycle helpers.
• Propagate PPL profile flag through transport and request parsing, enforce supported formats/paths, and document profiling usage.
• Capture per-stage metrics across planning, optimization, OpenSearch execution, and response formatting; add profiling teardown and update related tests/expectations.

Related Issues

#4294

Check List

• New functionality includes testing.
• New functionality has been documented.
• New functionality has javadoc added.
• New functionality has a user manual doc added.
• New PPL command checklist all confirmed.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff or -s.
• Public documentation issue/PR created.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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