ci-fairy: check merge requests for the allow_collaboration flag

Add a command to ci-fairy to check merge requests for various features. So far only one of those is available, the ability to check for the "Allow commits from members who can merge to the target branch." toggle to be enabled.

Ideally this can be added to the CI and ci-fairy will produce a junit.xml on request. see this test merge request in libevdev: libevdev/libevdev!55 (closed)

This MR was filed after the pipeline already succeeded but with the checkbox disabled. So, ideally, the CI status of the MR should be "failed". Let's see...