Consolidate tooling and pipeline config in CODEOWNERS

What does this MR do and why?

We have duplicated reviewers / maintainers for EP/tooling files. This MR consolidates the knowledge in CODEOWNERS, which is more future-proof and in the spirit of dogfooding.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.