Begin moving `script` boiler plate from YAML to shell scripts.
Initial (incomplete) migration described by #4194 (closed).
Improve maintainability and reusability of CI job logic by expressing in shell scripts instead of GitLab CI YAML.
If this change appears useful and works well in practice, we can migrate other YAML-embedded shell scripting as is necessary or convenient.
Refs #4194 (closed)
Edited by M. Eric Irrgang