This switches from the ansible/dhall operator framework to kopf,
an operator framework written in pure Python. This allows us to:
* Build the operator application as a Python app.
* Build the operator image using the opendev python builder images.
* Run the operator as a Python CLI program "zuul-operator".
* Write procedural Python code to handle operator tasks (such as
creating new nodepool launchers when providers are added).
* Use Jinja for templating config files and k8s resource files
(direct pythonic manipulation of resources is an option too).
The new CR nearly matches the existing one, with some minor differences.
Some missing features and documentation are added in the commits
immediately following; they should be reviewed and merged as a unit.
Also, fx waiting for scheduler to settle in functional test since
we changed this log line in Zuul.