A site developer of a Drutopia site can easily run PHP Unit tests

Problem/Motivation

Provide a patch or composer post-run script to automatically keep a working phpunit.xml file in place in web/core to work around the issue noted here:

📌 phpunit.xml is deleted when doing composer update Active

"If you are using Composer to manage Drupal core" as if this is something that only affects some people. That is not supposed to be an "if" in modern Drupal.

Proposed resolution

Possibly this belongs in drutopia-dev, but we may want regular sites to run the tests also.

Remaining tasks

User interface changes

API changes

Data model changes