Add codeowners file; update token permission to read only for workflow

[mythri-garaga]

Summary

This PR includes changes -

1. Added codeowners file to this repository.
   https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners
2. Reduced the token permission to read only by setting the the permission directive to read for workflows
3. Use a regular expression and validation to make sure that the GO_VERSION is of the correct format and length

Implementation details

Testing

Workflow logs shows correct Go version being used

Setup go stable version spec 1.18.3
Attempting to download 1.1[8](https://github.com/aws/amazon-ecs-agent/runs/8234162562?check_suite_focus=true#step:4:9).3...
matching 1.18.3...

New tests cover the changes:

Description for the changelog

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.