When a runner registers for a build, the JSON payload may require
loading a few Gitaly RPCs, which may fail. If these any of these fail,
the build will be appear as though it has been assigned to the runner,
but the runner will have received a 500 error and not proceed.

To recover from situations like this, we try to render the payload in
`RegisterJobService`. If that fails, we mark the job as failed with a
`scheduler_failure` so that it may be retried again.

This came out of https://gitlab.com/gitlab-org/gitlab/-/issues/227215.