EPIC: publish all our policies also as helm charts

[flavio]

TODO: to be refiened

All our policies should also be published as helm charts (one per policy), to simplify how the Kubewarden UI discovers their existence.

For that:

• [x] Amend RFC-10 and decide on the layout of kubewarden/helm-charts: either a folder in charts/ that gets published as a separate https Helm chart repo, or a separate branch. Check that the Helm chart repo can happen separately under GH Pages. https://github.com/kubewarden/rfc/pull/45
• [x] #1001
• [ ] Adapt the make generate-policies-file target and the scripts/extract-policies.sh script so that each policy chart ships a policylist.txt inside the Helm chart.
• [ ] Adapt make generate-changelog-files target and its script to build the correct changelog file.
• [ ] Develop a script that creates and updates policy charts. We intend to run this script in an automated way on each policy release:
  • Takes all needed policy annotations from metadata.yml and converts them into Helm chart annotations as specified in RFC-10. This script will be run regularly.
  • Generates the needed Chart.yml annotations that don't come from the policy metadata.yml, See RFC-10.
  • Takes the policy and provides a values.yaml with their known policy.spec values, including the spec.settings.
  • Generates the chart/templates/policy.yml from the template provided in the RFC-10:
    • fills the template.yml::metadata.annotations with the metadata.yml annotations for severity and category.
• [ ] Adapt the helm unittest tests into a test that checks the render of the template against different typical values.yml.