Fix: finalizers not set on ClusterExtension

[joelanford]

Another thing I just found. We setup finalizers in main.go, but then don't actually set them on the reconciler or call Finalize during reconciliation. I tried updating to do these things, but then the controller started panic-ing because the finalizer expects to finalize a BundleDeployment, but we are now trying to finalize a ClusterExtension.

Originally posted by @joelanford in #903 (comment)

[joelanford]

This was fixed by #941