Add the ability, to share Group Runners with merge requests
Proposal
I've forked a project in a group, to work on it without mull over the original project. After supplying a merge request back, the runners in the merge-request failed, because my fork isn't in the group, but since the target is the group's project and the group wants to verify, that everything is alright. The runners of the group should be useable to verify that.
When executing runners, the runners should run / look in the context of the target. Just like ADL for c++.