[Build] Migrate helm chart to helm repository

[mawandm]

Description
In order to make it easier for developers to deploy Nesis, we need a helm chart that is reachable outside this GH repository from a helm chart repository.

Detail
Having a helm chart in a dedicated repository makes it possible to integrate the deployment of Nesis in an automated fashion such CI/CD process.

Acceptance Criteria

• Delete the ./helm folder
• Delete the ./.github/workflows/test_helm.yml workflow file
• A helm chart in the https://ametnes.github.io/helm repository deployable with

   helm repo add ametnes https://ametnes.github.io/helm && helm repo update
   helm upgrade --install nesis ametnes/nesis