Run workflow job from container built from local Dockerfile

The feature jobs.<job_id>.container.image should be able to build an image from a local Dockerfile from the git repository, otherwise I have to create a job that first builds and pushes that image to a registry, for example.

And this is also not the best solution for workflows associated to pull requests, where you don’t want to be overwriting the image tag latest across multiple PRs, i.e. you have to identify the pull request somehow in the image tag to avoid that, which is also not easy because the github context (github.ref, github.sha, etc.) does not simply provide the PR number, you are only able to parse it on the job steps with jq, for example ($(jq --raw-output .pull_request.number "$GITHUB_EVENT_PATH")).