Improve helm chart testing and release process

[evegufy]

Description

Improve the testing of the helm chart by building the images for init containers and pushing them to the registry available within the workflow to then use those images for the test of the helm install.

Once that is enabled, also the release process should be improved to release the helm chart and build the pinned docker images in one workflow, see example

Benefits

• improved automated tests (as otherwise always need to be built before testing)
• improve release process (as otherwise the image build needs to be triggered in an additional step)