WIP: E2E project mirror github with pipeline

What does this MR do?

New EE E2E test scenario gitlab-org/quality/testcases#144 (closed) for a project imported from external source (github), pipeline is triggered with new changes detect from the external project (mirroring).

Note: Since we cannot import the same project more than once, this can only be run in non-live environments

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content