wait_for_motion: Refactor: Extract diff algorithm into MotionDiff class
wait_for_motion: Refactor: Extract diff algorithm into MotionDiff class

With the aim of potentially re-using this in `press_and_wait`.

stb-tester/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester