Add built-in project template test

What does this MR do?

Adds a test for built-in project templates.

gitlab-org/quality/testcases#102 (closed)

CE backport MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/32358

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content