This new filter allows test cases to manipulate what the kernel reports,
e.g. mark connected connectors as disconnected to emulate monitors
connecting and disconnecting.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2821>
Add a tiny library that sabotages errors in drmMode*() API calls. This
will be used to artificially trigger arbitrary errors, e.g. cause the
next commit to fail with EBUSY.
The three mocked methods are added as they will be used in a future
commit.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2854>