unit test duplicate object detection function

[kfox1111]

We need a test like:

helm template charts/spire --set spire-server.federation.tls.spire.enabled=false,spire-server.federation.tls.certManager.enabled=true,spire-server.federation.tls.certManager.issuer.acme.email=[email protected],spire-server.upstreamAuthority.certManager.enabled=true,spire-server.federation.enabled=true,spire-server.upstreamAuthority.certManager.ca.create=true

It currently renders ok in helm template, but has duplicate objects that would fail a kubectl apply. We need a generic function in the unit tests to look for rendered duplicate objects to make writing a test for this easier.