Redesign Encoder polling code

[Ezward]

Rewrite the encoder polling code to act like the mono encoder sketch I create for the DonkeyCar project. See https://github.com/autorope/donkeycar/tree/921-next-generation-odometer-parts/arduino

The mono encoder does a reasonable job of reading encoder pulses while debouncing, all without interrupts. We can leave the interrupt version of the code as-sis.