Print total predicted number of buffer underruns

I think this is the final metric that we'll want to track.

Contributes to issue CURA-5561.

tests/50_inst_per_sec.py

@@ -501,6 +501,7 @@ class CommandBuffer:
                 code_count = item["cmd_count"],
                 time = round(item["time"], 4),
                 speed = round(item["cmd_count"] / item["time"], 2)))
+        print("Total predicted number of buffer underruns:", len(self._bad_frame_ranges))
 
 
 if __name__ == "__main__":