wlr_frame_scheduler: Add predictive frame scheduler

The predictive frame scheduler builds upon the presentation scheduler,
adding a delay based on the measured CPU and GPU time required to
prepare a frame to place the frame event as close as safely possible to
the commit deadline.

render/wlr_renderer.c

@@ -329,6 +329,9 @@ int wlr_render_timer_get_duration_ns(struct wlr_render_timer *timer) {
 }
 
 void wlr_render_timer_destroy(struct wlr_render_timer *timer) {
+	if (!timer) {
+		return;
+	}
 	if (!timer->impl->destroy) {
 		return;
 	}