Merge branch 'async-master' into 'master'

Draft: render,types/wlr_shm: Offload slow cleanup ops

See merge request wlroots/wlroots!4755

include/util/cleanup.h

@@ -0,0 +1,10 @@
+typedef void (*wlr_task_cb)(void *data);
+
+struct wlr_task {
+	wlr_task_cb task;
+	void *data;
+};
+
+void wlr_cleanup_queue_init(void);
+void wlr_cleanup_queue_finish(void);
+void wlr_cleanup_defer(struct wlr_task t);