Conditional controllers with event handler removal

[kevindelgado]

A proof-of-concept for how controller-runtime controllers could operate regardless of if the CRD they are watching is installed/uninstalled/reinstalled.

This builds off of two other WIP PRs in upstream k/k

1. Adding the ability to remove event handlers (support removal of event handlers from SharedIndexInformers kubernetes/kubernetes#98657)
2. Notifying the EventHandlers that when the list/watch call encounters an error by adding OnError to the EventHandler interface ([WIP] Add OnError to ResourceEventHandler kubernetes#2)

There are three new mechanisms at play here to make this work:

1. The controller's logic to start the watches is wrapped in a loop that will periodically re-check if the resource to watch can be installed and only starting it if it can be.
2. An ErrorFunc is added to the event handler that removes the event handler in the situation where list/watch is erroring out, because the CRD is not installed.
3. The informer is ran with stop options to indicate that it should shut itself down if all its event handlers have been removed.