Replace shell scripts with Ansible. #T434466

As part of https://phabricator.wikimedia.org/T434466, I figured that it would be simpler to replace ad-hoc shell scripts with Ansible playbooks.

Why? Because Ansible allows centralized configuration of connection parameters in a way that multiple maintainers can easily use. For example, it can ensure that any scripts executed connect to the correct Toolforge server, and that the commands run as the tool account. Doing all this in shell scripts would be a lot of extra code/overhead/complexity.