Be better at guessing Python package names for OpenAPI jobs

This issue arose out of a teams discussion

Currently, unless configured otherwise, OpenAPI client libraries use the GitLab project name as their package name. We often use "kebab-case" in our project names which is incompatible with Python module names. Either:

• add a rule to the Python OpenAPI jobs to only enable themselves if the Python package name is valid, or
• preferably, update the build jobs to convert from "kebab-case" to "underscore_case" automatically.