Add GitHub Copilot Connection and associated dashboards

[ewega]

⚠️ Pre Checklist

Please complete ALL items in this checklist, and remove before submitting

• I have read through the Contributing Documentation.
• I have added relevant tests.
• I have added relevant documentation.
• I will add labels to the PR, such as pr-type/feature-development, etc.

Summary

Adds a new gh-copilot plugin that ingests GitHub Copilot usage metrics (org + enterprise + user breakdowns) via GitHub’s Copilot Usage Metrics Reports APIs, including:

• Backend plugin: connection/scope/scope-config APIs, collectors/extractors, tool-layer models + migrations, tests, and e2e fixtures.
• Config UI: GitHub Copilot connection UI (org/enterprise fields) and related validation.
• Grafana: Copilot Adoption and Copilot + DORA Correlation dashboards.

Does this close any open issues?

Closes #8664

Screenshots

Plugin/Connection

GitHub Copilot Adoption dashboard Screenshot

GitHub Copilot + DORA Correlation Dashboard Screenshots

PR velocity impact: adoption vs cycle time

Adoption intensity: tier distribution and trends

Deployment + change failure rate impact

MTTR + code review time impact

Other Information

• go test ./backend/plugins/gh-copilot/... passes locally.

[klesh]

Thank you for your contribution!
Could you please take a moment to fix the checks? Thanks so much.

[ewega]

@klesh Thanks! I proposed some fixes to CI. Hopefully it passes now

[klesh]

Great job! Thanks for your contribution.