Define code ownership using "OWNERS" files in the central CI config repo

[wuhuizuo]

In order to improve the code review process and ensure that changes are reviewed by the appropriate people, we propose using "OWNERS" files to define code ownership in our central CI config repository. This repository contains Jenkins pipelines, shell scripts, and Jenkins job DSL files that are used across multiple development teams.

By defining code ownership using "OWNERS" files, we can:

Ensure that changes are reviewed by the appropriate developers who are familiar with the codebase
Reduce the burden on individual maintainers to review all changes
Improve the quality of the codebase by ensuring that changes receive appropriate scrutiny
We propose creating an "OWNERS" file for each subdirectory in the repository that corresponds to a different team or area of the codebase. Each "OWNERS" file will contain the GitHub usernames or team names of the developers who are responsible for that code.

We also propose configuring our CI system to enforce the use of "OWNERS" files. This means that pull requests will not be able to be merged until they have been approved by at least one owner of the affected code.

We encourage all development teams to review this proposal and provide feedback. We also ask that each team review their respective codebase and provide a list of owners who should be added to the corresponding "OWNERS" file.

Thank you for your time and consideration.

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Some tasks need to be finished:

• setup "OWNERS" files for documents CI files. #2975
• setup "OWNERS" files for TiDB CI files.
• setup "OWNERS" files for TiFlow CI files.
• setup "OWNERS" files for TiFlash CI files.
• setup "OWNERS" files for PD CI files.
• setup "OWNERS" files for TiKV CI files.
• more...