test: Add assertion for OpaCluster in iceberg test

Author: sbernauer

tests/templates/kuttl/iceberg/31-assert.yaml

@@ -0,0 +1,5 @@
+apiVersion: kuttl.dev/v1beta1
+kind: TestAssert
+timeout: 300
+commands:
+  - script: kubectl -n $NAMESPACE wait --for=condition=available opaclusters.opa.stackable.tech/opa --timeout 301s