Create wlroots-based autotests compositor

[romangg]

With !8 we have a feature based on a wlroots protocol and this feature is only available in the Wrapland Client library. Because of that autotesting is difficult. A wlroots-based compositor in our testing infrastructure could be introduced to test this feature.

But also in general it would make sense to have such a compositor so we can test this and other interfaces against another protocol implementation what makes our testing more meaningful.