Update the Helm Operator to v1.2.0

This adds `helm test` integration as well as several bug fixes.

Release notes:
https://github.com/fluxcd/helm-operator/releases/tag/v1.2.0

The CRD updates were already included with the v1.1.0 change [0]
which was fine since they were backward compatible.

[0]: https://review.opendev.org/#/c/720298/

Relates-To: #343
Change-Id: If68297c9de347c1c95e68e1bbb6deeb0bded7678

manifests/function/helm-operator/deployment.yaml

@@ -23,7 +23,7 @@ spec:
       containers:
       - args:
         - --enabled-helm-versions=v3
-        image: docker.io/fluxcd/helm-operator:1.1.0
+        image: docker.io/fluxcd/helm-operator:1.2.0
         imagePullPolicy: IfNotPresent
         livenessProbe:
           httpGet: