Use chromeos label for chromeos.kernelci.org

[gctucker]

The deploy.py script can pull together PRs for a particular target branch, such as main for staging.kernelci.org and chromeos for chromeos.kernelci.org. It would be good to add an option to also pull PRs that have some particular label(s), for example to have a single PR deployed both on staging and chromeos instances. That way, the code would be directly available on both and there won't be a need to first have it merged on chromeos and then port it to main or first merge it on main and then rebase chromeos.