User-facing Chrome-Infra services

• Commit Queue (CQ): verifies and lands CLs. This will be replaced by LUCI Change Verifier (CV).
• gsubtreed: mirrors a subdir of a Git repo to another Git repo.
• luci-config: Project registry.
• Buildbucket: simple build queue.
• Tree status: prevents CLs from landing when source tree is broken.
• Monorail: The issue tracking tool for chromium-related projects.
• Code Search: Searches code and navigates code.