Catch post-submit issues before creating draft release

We can easily miss build issues in the post-submit jobs. If a build fails and we later try to make a release from that same commit, we get no release artifacts.
We should try to include a check in the release workflow that would detect these issues. I am fairly sure it is possible to get the "status context" of a specific commit. If we can check that on release note PRs then we can block accidents.

What post-submit build am I talking about? You can see it at the top of any commit page, e.g. here: https://github.com/kubernetes-sigs/cluster-api-provider-openstack/commit/2bfcd2a48b296963191238d2411643bb73179297. There is a little ✔️ 1/1. That links to the build.

Start by locating the release workflow and examining how release note PRs are handled. Inspect the status context linked from the example commit to determine how post-submit build results can be checked. Done means a failed post-submit build is detected and the release is blocked before artifacts are missing.

Written by the indexing model from the issue text.