Add a unit test for wlr_box and benchmark for wlr_scene_node_at as our first test examples, lowering the barrier for adding more tests as suitable.
udmabuf can create a DMA-BUF backed by a memfd. This is useful when running with a software implementation of GL/Vulkan: the memfd can be passed to the parent compositor via wl_shm and the DMA-BUF can be imported via the usual APIs into GL/Vulkan.
This is the preferred name since Meson 1.1.