Draft: backend/drm: Expose WLR_DRM_NONBLOCKING_MODESET
There's a report of issues with amdgpu and the new nonblocking modeset. Rather than a rollback, we could consider making it temporarily configurable until the issues have been resolved.
I wonder if we should expose an opt-out instead.
Draft as the original issue have not yet been debugged, just threw the code together for now.