[stable29] test: re-add object store primary storage phpunit tests

[backportbot[bot]]

Backport of #48235

~~Warning, This backport's changes differ from the original and might be incomplete ⚠️~~

Todo

• [x] Review and resolve any conflicts
• [x] Amend HEAD commit to remove the line stating to skip CI

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.