Clean up github actions

[kravciak]

Unused github actions / workflows:

• https://github.com/kubewarden/kubewarden-end-to-end-tests/blob/main/.github/workflows/e2e-tests.yml
• https://github.com/kubewarden/github-actions/tree/main/setup-kubewarden-cluster-action

Possible replacements:

Actions were used to create k3d cluster and import custom images. We don't test this currently, possible replacement would be to:

• extend helmer scripts to handle custom image import
• expose helmer scripts as github actions to provide partial functionality, for example:
  • create custom k3d clusters
  • install custom kubewarden versions
  • install custom rancher versions