Remove operatorkit dependency from etcd-backup-operator

[JosephSalisbury]

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[JosephSalisbury]

fyi @yulianedyalkova

we want to get rid of operatorkit at some point, etcd-backup-operator still uses it

there's some toss up here between rewriting the operator in kubebuilder, or possibly it just makes more sense to move to something like velero. happy to chat about it

i'd like to get this done, but there's no real urgency, it's more on the technical debt side