Deduplicate hetzner-ci.yaml and hetzner.yaml

[guettli]

/kind feature

The files test/e2e/config/hetzner-ci.yaml and test/e2e/config/hetzner.yaml are very similar.

I think we should de-duplicate these files:

1. Create the common base as hetzner.yaml
2. Do modifications which are needed for hetzner-ci.yaml "on the fly" during ci.
3. Delete hetzner-ci.yaml from the git repo.

During the last months I was confused by that several times.

CI overwrites it like this:

        E2E_CONF_FILE_SOURCE: "${{ github.workspace }}/test/e2e/config/hetzner-ci.yaml"

file: .github/actions/e2e/action.yaml