Add helm test functionality

I'd like to introduce helm unittests unit tests into the umbrella Helm chart. The umbrella chart contains a ton of logic that could be verified prior to any Kubernetes deployment.

• The checks could execute with multiple values.yaml variations quickly and sanity check the output.
• It would also more obviously capture the intended output.
• It would protect us from regressions when doing non-functionality based refactors of helpers or templating logic

As a huge caveat to suggesting the helmtest plugin specifically - another possible outcome is leveraging an existing programming language's test framework to write tests without a plugin. There are reasons why that might be easier and more flexible ultimately.