Create testing for package_name validation schema

Problem/Motivation

Follow-up to 🐛 Package name schema regex is not validated Fixed

In the issue we fixed the regex for the package name config but for some reason in core pre 11.x this does not cause a test failure.

That merge request had tests that will fail in 11.x as expected but not in 10.1.x

This issue would be to add the test coverage back.

Steps to reproduce

Proposed resolution

Add the test coverage back either

1. After the core merge request is committed(in which case this should be move to drupal core issue queue) or
2. after we no longer support 10.1.x(hopefully 😬 1) happens first