Set up GitlabCI for the 8.x.1-x branch

Committed the changes and I can see some failed tests: https://git.drupalcode.org/project/commerce_paykings/-/pipelines/465883

I'll open another issue to fix these, for now I'll mark this issue as "Fixed", if anyone has any issues, please let me know and I'll re-open the task.

I allowed all tests to fail, in order to allow the MR to be merged.

Automatically closed - issue fixed for 2 weeks with no activity.