Run GDK tests with Gitaly transactions enabled for Gitaly upgrade MRs

Similar to the Omnibus job: gitlab-org/gitlab!152388 (merged)

This will allow us to prevent bugs relating to Gitaly transactions before merging more promptly than having to wait for Omnibus pipeline to finish.

• Run full GDK suite with Gitaly transactions off (currently being done) and on
• Run in parallel to the existing GDK pipeline

This issue was created after slack discussion, where a gitaly failure was not picked up by the current gdk suite: