Support --pattern=addon flag that generates an addon operator

[justinsb]

Creates a controller & resource that follow the style of
https://github.com/kubernetes-sigs/kubebuilder-declarative-pattern

These style of declarative addon operators are being investigated in
the cluster-addons subject, with code at
https://github.com/kubernetes-sigs/addon-operators

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[johnsonj]

We discussed this in the kubebuilder and controller-runtime meeting today. @DirectXMan12 is going to take a look and see if the plugin model they've been considering would take care of this use case and propose it if it does.

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[DirectXMan12]

closing this -- it merged as part of the plugins PR