This simplifies the event listener sink by adopting the knative eventing "adapter" library, which is like our sharedmain for controlplanes, but for the eventing dataplane components.  This pattern passes config data as JSON in `env:`, so it also dramatically simplifies the controller logic because we no longer need to copy around empty configmaps and clean them up, and net removes a lot of code.

This also takes advantage of the new dynamic client injection logic to reduce the overhead of each adapter on the API server, and potentially dramatically improves cold start time of ksvc based sinks (they no longer need to sync informers to handle traffic).  If this proves troublesome, it should be relatively straightforward to switch things back.