Migrate Flux lab to use sample app Helm charts

[niallthomson]

What would you like to be added?

Now that there are Helm charts available on ECR Public for the sample application we should use these for the Flux lab.

Why is this needed?

The current way the Flux lab works requires a lot of copy/pasting of manifests and kustomize stuff. This is more confusing that it needs to be. Referencing the Helm charts would be a more streamlined way to approach teaching this subject.