WIP: Add CiliumNetworkPolicy resource and related tests

Add CiliumNetworkPolicy resource and related tests. With the addition of Cilium the dependencies require updating Terratest which in turn requires Helm 3. It seems that if Helm 2 supported --show-only updating to Helm 3 could be postponed at least.

Another option would be to add this resource without unit tests while relying on the manual ones.

I am open to suggestions.

With the new version of Terratest/Helm, tests cases will fail if template is not provided. Therefore a positive guard condition is required as a minimum to have the tests running. Also there is a maximum length (i.e., 53) set for the chart name which required a couple changes.

Lastly but not least, if we decide to move forward with the first option a image with helm 3 will have to be used for the test instead of relying on the same build of alpine-helm.

Related issue: gitlab-org/gitlab#223623 (closed)