feat(observability): add job level streaming cpu profilling

[EdwinaZhu]

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What's changed and what's your intention?

This PR adds job-level CPU usage observability for streaming jobs by aggregating existing actor-level Tokio poll duration metrics.

Previously, CPU-related metrics were only available at the fragment level #23747, making it hard to understand resource usage from a job perspective. This PR uses PromQL to aggregate poll duration from fragment → job level, and updates Grafana dashboards under Streaming section.

The goal is to provide a lightweight and practical view of CPU usage at the job level, helping users quickly identify CPU-heavy streaming jobs and diagnose performance issues.

Checklist

• I have written necessary rustdoc comments.
• I have added necessary unit tests and integration tests.
• I have added test labels as necessary.
• I have added fuzzing tests or opened an issue to track them.
• My PR contains breaking changes.
• My PR changes performance-critical code, so I will run (micro) benchmarks and present the results.
• I have checked the Release Timeline and Currently Supported Versions to determine which release branches I need to cherry-pick this PR into.

Documentation

• My PR needs documentation updates.

Release note

[kwannoel]

Could you share some screenshots of how this panel looks?

[EdwinaZhu]

#23747

@kwannoel this is the screenshot of the panel.